Building a Garden Pond for Aquatic Insects, Part 4

pondWater, Electricity, and Avoiding Skeeters!

Now that I’ve gone over how I installed my pond at the Biosphere 2 and the things I added to it to keep the water nice and the bugs happy, I wanted to discuss a few final things: keeping my pond low-maintenance while keeping the water clean and mosquito-free.  In the interest of keeping this post within my personal word limit, I’ll finish up the pond series in my next post with some brief info about the display as a whole and the educational experience that my pond represents.

I live in a desert.  By definition, a desert is a place where there is more evaporation than precipitation, so any time you expose water to the air it tends to dry up.  Having to top the pond off every day wasn’t going to work because the Biosphere 2 doesn’t have the personnel available to do it.  Instead, I installed an automatic filling system so that the pond would refill whenever the water levels dropped so that no one will need to keep an eye on the water levels.

This was a rather simple task.  The B2 staff extended a water line from the agricultural module into the courtyard where my pond is located.  All I had to do was connect the 3/4 inch PVC pipe they left (and dug a trench for – thanks to the B2 maintenance staff for the help!  I really appreciate it!) to my pond via a simple float valve, the kind commonly used in evaporative coolers.  So, I made a trip to Home Depot and bought the supplies: a float valve, an threaded PVC connector, some PVC glue,  several brass adapters that would connect the 3/4 inch PVC connector to a 1/4 inch plastic hose (including a compression fitting), and teflon plumber’s tape.

float valve

My pond's plumbing. The float valve is the blue float in the background and you can see the hose connector on the outside of the tank.

I fitted the PVC connector onto the PVC pipe with the glue and let it sit overnight.  The next day, I wrapped all of the threads of the adapters with teflon tape and screwed them together and onto the PVC connector.  I then ran the hose up the side of the tank and connected it to the compression fitting on the float valve.  Finally, I inserted the float valve through a hole I drilled into the tank (okay, the second hole – I completely screwed up the first one, as you can see in the picture…) and turned the water on.

And got sprayed right in the face while I scrambled to turn the water back off.  After several more attempts to get the hose properly attached to the compression fitting on the float valve (let’s just say it was more than 10 attempts and leave it at that), I got everything connected and didn’t have any leaks.  I buried the pipe and the hose, piled a bunch of rocks up along the exposed part of the hose on the outside of the tank, and adjusted the float valve to fill the tank to the level I chose.  Now, every time the water level drops below that level, it opens the water valve, filling the tank automatically!

In spite of the problems I had getting the float valve and the hose connected properly, it was pretty easy to do the plumbing for the tank.  If you choose to build a pond at home, an automatic filling system seems to be an easy way to save yourself a lot of maintenance on your pond.  If you have a spigot that can be devoted to your pond, it is very easy and cheap to connect a float valve to it using the same method I used for my pond without doing any major plumbing work – you just leave out the PVC parts.  If you don’t have a spigot available, you will need to extend a pipe specifically for your pond and connect it to a float valve for automatic filling.

pump housing

The housing for my pond pump. You can't see the rock under the pump, but it's there.

The other thing the B2 staff had to do for me was extend an electrical line from the agricultural module so that I could install a pump to keep the water flowing in the pond.  You don’t have to have flowing water, but there are several reasons why you might want to.  For one, it circulates the water and causes turbulence.  This helps boost the oxygen level of the water: the more turbulence, the greater the oxygen load of the water.  I also wanted to maintain flowing water to avoid breeding mosquitoes, but more about that in a moment.

If you read my last post, you know that I stacked some cinder blocks to build a housing for my pump.  I did this so that the pump would be largely enclosed to reduce the amount of debris that might clog it.  I put a rock at the bottom of the cinder block column to keep the pump off the ground so that the silt that settled on the bottom of the pond wouldn’t get sucked into the pump and redistributed into the water.  I connected the tubing to the pump and dropped the whole thing into the housing, trimming the hose so that it extended about 10 inches above the proposed water level.  Once I filled the pond up, I stacked flat rocks over the top of the pump housing, partly to keep debris from falling into the housing, but also to provide something for the water to run over.  The tube from the pump ends just out of sight under the top rock.  This is the result:

pond waterfall

The waterfall in my pond. You can see the water flowing out of the pump's hose in the center of the image.

I think it looks rather pretty, but the mosquitoes are the main reason I though a pump was essential.  Mosquitoes are a big problem in Arizona and are attracted to water to lay their eggs.  Fortunately, there are several ways you can prevent mosquitoes.  First, mosquitoes don’t like to lay their eggs in moving water, the rationale behind the pump.  Mosquito eggs are susceptible to being washed downstream and the larvae don’t like flowing water, so female mosquitoes generally only lay eggs in still water.  My pond pumps about 300 gallons (over half of the volume of the pond) per hour.  This is enough to keep the water moving across the entire surface of the pond at all times.  Second, mosquitoes don’t like to lay their eggs in direct sunlight, as I recently learned from a mosquito biologist who works in my department.  My pond is in full sun for about 6 hours a day.  Third, you can use BT rings to kill mosquitoes in the pond as necessary, though these will also kill the other fly larvae  and potentially some of the beetles growing in the pond.  BT is the colloquial name for the toxin that the bacteria Bacillus thuringiensis produces.  This toxin readily kills a narrow range of invertebrates, including flies, butterflies and moths, some ants, bees, and wasps, and some beetles.  It has been used in powder form as an alternative to pesticides in organic farming and has been genetically engineered into the genome of several crop species (including cotton and corn) to decrease the amount of pesticides used fighting agricultural pests.  Since mosquitoes are flies, dropping BT ring pieces into the pond now and again should keep mosquitoes in check.

One final method for controlling mosquitoes involves a biological control method: mosquitofish (Gambusia affinis).  While many pond enthusiasts favor using fish in the war against mosquitoes and in spite of the fact that mosquitofish are very effective mosquito larva predators, I didn’t want to use them in my pond.  They aren’t native to Arizona and I believe they are problematic are in many of our waterways, so I am opposed to using them in case they are accidentally spread to new systems (it happens).  If I have fish in the pond, it will also drive the nitrogen levels, ammonia in particular, to levels that require control.  This involves installing a filter, which further requires swapping out filters, making sure it’s working properly, testing the water for ammonia, etc.  That is much more maintenance than my pond will receive.  So, it worked out that adding the fish I don’t like anyway wasn’t feasible with the low-maintenance requirements of my pond.  I am relying on the other three methods instead.  An added benefit of building a pond to attract insects is that it will attract several mosquito hunting insect predators as well, including giant water bugs, dragonflies, and backswimmers.  The very insects I hope to attract to my pond might control the mosquito population themselves!

Next time I’ll complete my pond series with a brief look at the educational components of my pond, including the identification guides I developed.  Seeing as educating the public about aquatic insects was the whole point of building the pond, I thought the topic deserved its own post.  I hope you’ll check back!

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Unless otherwise stated, all text, images, and video are copyright © 2010 DragonflyWoman.wordpress.com.

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Building a Garden Pond for Aquatic Insects, Part 3

pondChoosing and Installing Substrates

Last time I discussed how I chose a location, planned, and installed the container for the pond I recently built at the Biosphere II.  My pond is designed to be low maintenance and attract aquatic insects, so the things that I chose to put into the pond were important – different insects look for different things when choosing a home.  Today, I’m going to go over the things I chose and why I chose them.

There were two main things that I wanted to balance in my pond: diversity of insects and the quality of the water.  Many insects depend on a particular water quality to survive, but the pond is also an educational display.  Being able to see into the water is a good thing if you’re trying to convince people to look for the bugs!  I also wanted to provide many different objects in the water to attract as many different types of insects as possible.  Choosing the right plants and ornamental/landscaping features are important if these are your goals.

I started by adding a tick layer of pea gravel, small cobble, and large cobbles to the bottom of the pond (large cobbles not pictured):

pond rocks

Rocks in the bottom of the pond.

Many insects like to sit on the bottom of ponds and want things to hold onto.  There are several species of insects that I find only on rocks, so I wanted to make sure there were plenty available.  By including three different sizes of rocks, I created 3 different habitat types that might attract three or more different types of insects.  These rocks were also very dusty and I knew I would end up with a layer of fine sand or silt at the bottom of the pond once it was filled, creating yet another space in which some insects will live.

Next, I added the cinder blocks you see in the image.  These were installed to provide a platform onto which I could later put my plants.  I also needed to create a space that would be relatively silt-free in which I could put the pump that would circulate the water.  I’ll talk about the pump in my next post.

My field site!

An example of a natural pond experiencing a massive algae bloom.

Many people install a layer of garden soil on the bottom of their ponds so that they can plant plants directly into the pond.  While this most accurately imitates a real pond, I didn’t want to do this for one important reason: adding a lot of garden soils to the water introduces nutrients into the water.  While these are good for promoting plant growth, something you might desire if you are building a pond for growing plants rather than attracting insects, putting a lot of soil in ponds drive nutrient levels up.  This in turn promotes algae growth and can cause massive algae blooms (rapid reproduction and growth of algae) and causes problems in the pond.  Algae blooms tend to make the water very opaque (see image at right), which decreases the educational value of my pond.  The algae can also block the light from reaching any submerged plants near the bottom of the pond, potentially killing them.  Further, when the algae absorb most of the nutrients from the water, they die off in hoards, fall to the bottom of the pond, and rot.  The rotting process consumes oxygen, so the oxygen levels in the pond drop.  Sometimes this can kill the insects that live in the pond.

You can control algae with algaecides, but that is a maintenance heavy task and my pond needed to be low maintenance.  Instead, I decided not to put much garden soil into the pond to keep the nutrient load as low as possible.  Many aquatic plants can survive in rather low nutrient environments, so I planted the rooted plants in pots, then submerged the pots in the pond.  This had the added benefit of allowing me to keep the plants contained so that they wouldn’t spread and fill the entire pond.

Horsetail

One of my plants, a horsetail reed, in its pot.

I bought some of my plants (including the horsetail at left) and those all came pre-planted in soil.  For the plants that were donated and/or harvested, I largelyfollowed the recommendations of the Tucson Water Gardeners and used unscented kitty litter in place of soil and planted my plants in water plant baskets that I got from Home Depot.  I added a thick layer of kitty litter, a very thin layer of garden soil, and finished with a thick layer of kitty litter on top.  This way, the soil is held in place by the litter (soil can float to the surface if it’s not weighed down) and there is very little soil added to the pond, but enough nutrients for the plants to thrive.  I’ll give an update on how my plants are faring next month when I know how well it worked!

I wanted to include a variety of plants in my pond.  This makes the pond look nice, but the right balance of plants also contributes important habitat to a variety of aquatic insects and helps keep the water looking its best.  For the insects, I wanted to use several different types of plants: rooted marginal plants (those that have their roots in the water and the vegetation extends well above the surface), floating plants (rooted or unrooted plants that float on the surface), and submerged plants (plants that are entirely underwater).  The rooted marginal plants provide vertical habitat for insects that like to climb, such as damselfly nymphs.  Floating plants are great for obscuring insects that swim in the water column like beetles and backswimmers.  The submerged plants are great habitat for the insects that stay underwater all of the time and like to hide, such as mayflies.  Lots of different types of plants mean lots of different types of insects, so including a variety of plants was a priority for me.

The plants also contribute to the quality of the water in the pond in several important ways.  Submerged and floating plants contribute a lot of oxygen to the water as they photosynthesize, something the insects, especially those that live on the bottom of the pond and don’t go to the surface to breathe, need to survive.  (For more information, see my posts on aquatic insect respiration and improving aquatic respiratory efficiency.)  All of the plant species absorb nutrients from the water, keeping the nutrient levels down.  The plants also block the light from about half of the pond.  Low nutrients and low light are good things if you want to keep the algae population under control, so hopefully my plants will prevent huge algae blooms from occurring in my pond.

As far as the specific plants I used go, I used 9 different species.  For marginals, I used horsetails (Equisetum hyemale – an interesting plant), cattails (Typha latifolia), arrowhead (Saggitaria sp.), an unidentified rush species, and a yellow water iris (likely Iris pseudocrorus).  My floating plants include an unidentified floating plant I got from the University of Arizona’s Environmental Research Lab and parrots feather (Myriophyllum aquaticum – an invasive aquatic plant commonly sold as a pond plant that I only planted because it is FAR away from natural water sources).  My submerged plants are a type of hornwort (Ceratophyllum sp.) and a waterweed (Elodea sp.).  All of these are supposed to thrive in Tucson’s climate, so we’ll see how well they do at a slightly higher elevation.  (Thank you to the Tucson Water Gardeners for donation of the hornwort, waterweed, parrots feather, and arrowhead, and to the UAERL for the irises and unidentified rush and floating plant!)

I filled up the pond with a hose and put the plants in their pots into the pond.  The water was muddy when it was first filled, but the silt settled out pretty quickly – the water was clear a few days later when I went back to B2 to work on it again.  Good thing, because it didn’t look so great at first:

muddy pond

My pond, immediately after filling.

If you read my last post, you know that I had to make my pond safe for kids to be around, which involved installing a barrier.  The mesh you see just under the water is what I call the anti-drowning shield for my pond.  It’s not pretty and it was a beast to install (the worst part my the experience!), but it keeps kids out of the pond too.  It’s a good thing and necessary.

Next time I’ll talk about my pump, installing the water and the electrical components for the pond, how I’m combating mosquitoes, and the educational components of my display.  Later this month I’ll give an update on how my pond’s doing!  Hope you’ll check back!

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Unless otherwise stated, all text, images, and video are copyright © 2010 DragonflyWoman.wordpress.com.

Building a Garden Pond for Aquatic Insects, Part 2

pondChoosing a Pond Location and Installing the Container

As promised, today I’m going to talk about choosing a site and installing the water container for an aquatic insect garden pond.  I think this was the hardest part of the process for the pond I built because it involved the majority of the planning and manual labor.  Once you get through these parts and get the substrates in, you’re basically done!

My pond was installed at the Biopshere II, so the first step was getting the project itself and the location approved by a committee.  If you are a homeowner, you should check your city ordinances for any regulations and restrictions regarding water features in your yard.  For me, the requirements were that the pond had to be a) low maintenance, b) at least partially above ground to keep people from falling in, and c) covered with something that would prevent children from drowning if they fall in.  These restrictions actually made every step harder than it might have been otherwise, but you have to work within the guidelines you are given.  Many cities require fences around ponds larger than a certain size or other safety features.  Be sure you follow the guidelines for the area in which your pond will be installed, especially if it’s going to be a large pond!

The next step was designing the pond.  When designing my pond, I decided to keep it simple.  I wanted the pond to be fairly small so that it would be reasonable to install within the time I had available and wouldn’t require a huge amount of water to fill.  (I do live in a desert after all!)  I wanted about 2/3 of the area to be open so that people could look into the pond and try to find aquatic insects, but 1/3 needed to be plants to keep the water properly oxygenated, absorb nutrients produced by things that fall to the bottom of the pond, and provide habitat for insects.  I decided which structures I wanted to put into the pond to make it as attractive to as many different aquatic insects as possible (the subject of my next post).  I also decided to have the pond self-fill to keep the maintenance level down.  This is about as basic as a pond gets, which was perfect for my needs.  However, you can make ponds that are quite elaborate.  You can add waterfalls, streams, filters, and all kinds of other features to make your pond look nice.  Some pond enthusiasts build ponds for fish or specific types of aquatic plants (such as water lilies) or use their ponds to raise frogs.  I have a single purpose for my pond – attracting aquatic insects – so I designed the pond to be appropriate for my needs.  If you are more concerned about aesthetics, you should consider some of the more complicated designs so your pondwill look pretty AND attract bugs to your yard!

Next, I chose a spot for my pond.  After moving having my pond’s location moved a few times by the Biosphere staff, I was finally assigned a spot, this courtyard:

Orchard Courtyard at Biosphere II

Orchard courtyard at Biosphere II

This space is outside the western part of the orchard area of Biosphere 2, the orchard courtyard.  Within this space, I was allowed to choose my exact spot.  My colleague had chosen her spot first, so I chose the area across the courtyard.  When choosing my exact spot within this space, I considered the following things:

— How level the area was.
— How hard it would be to move the things in the location (rocks, dirt, plants, roots, etc) to install the container that would become the pond.
— How much sun the area would get.  This is important when you consider what kinds of plants to use in the pond and the kinds of insects you wish to attract.
— How many trees were likely to lose leaves that would fall into the pond.

Moving more things than you have to is never fun, so I chose a location that was mostly flat already and only needed to have one large rock removed to work.  The area would be in the full fun for several hours a day, but not the entire day, so I could use plants that required full sun or partial shade in the pond.  Leaves are the enemy of any low maintenance pond because they accumulate quickly and need to be removed periodically, so I was very thrilled to find a space that didn’t have any overhanging trees and was unlikely to get many leaves blowing into it.  I think my site is about perfect!  That’s it in the image below.

Site of pond

Site of pond, before installation

The next step for me was choosing the container for my pond.  There are several options to consider.  Perhaps the most aesthetically pleasing is an in-ground pond.  To make these, you dig a hole and line it with either a flexible pond liner (the cheaper option) or a pre-formed plastic shell (the easier option).  I had originally wanted to do this, but the above-ground requirement imposed by B2 made this impossible – you can’t hold water above ground level with an in-ground pond!  (Good thing it didn’t work out anyway because it was nearly impossible to dig in this area without heavy digging equipment like a backhoe.)  In the end, I chose to use a stock tank, the kind you find at feed stores to water livestock.  Stock tanks are nice because they’re lightweight, they’re reasonably priced, and they’re durable, so they’ll last a long time.  You can also buy above ground plastic containers, but they’re likely to be more expensive and can disintegrate faster, especially in very warm or very cold areas.  My pond was created from a 6 foot diameter, 2 foot deep aluminum tank:

Stock tank

Stock tank for use as the container for my pond

I moved the stock tank from the top of my car to the bed of a friend’s pick up truck and we drove it out to B2.  Once there, installing the stock tank was very easy.  The big rock was moved so the tank would exactly fit into the space.  Because we were putting in an above-ground pond, we simply moved some of the larger rocks, leveled out the site out with a pick axe and shovels , rolled the tank up the ramp to the courtyard, and plopped it into place.

The two of us didn’t have any trouble at all getting the tank into place (and my friend is a very tiny woman), so this is something that I think anyone could easily do in their yards.  If you’re digging a hole and using a liner, you might want a small crew of diggers to help you out – or rent a small bulldozer or tiller to get everything loosened up and pulled out more quickly.  I’m personally pleased with how easy it was to get the tank installed and I’m happy I wasn’t allowed to do an in-ground pond.  It would have been so much more work!  The tank perhaps doesn’t look as nice as an in-ground pond, but the aesthetic gains don’t seem worth the extra time and energy to me.  Besides, once my pond has some landscaping done and rocks are piled up around the outside of the tank, it’s going to blend in well and look great!

Next time I’m going to talk about selecting substrates – plants and other features – to attract a variety of aquatic insects.  Check back soon!

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Building a Garden Pond for Aquatic Insects, Part 1

pond

My aquatic insect pond

As part of the fellowship I have from the Biosphere (the one that prompted me to start this blog), I designed a permanent educational display that will be available to visitors to the Biosphere.  Because I am an aquatic entomologist, I wanted to introduce people to aquatic insects, especially those that are found in the Sonoran Desert.  I think this is important because most of the people I’ve talked to in the area a) don’t think there’s any water in the state and b) certainly never considered the possibility that there might be insects in that non-existent water.  Yes, Tucson and the Biosphere are in a desert and yes, that means it’s dry, but there IS water – quite a lot of it in fact!  And that water, especially when clean and cool, is home to tons of insects.

I love to teach people about aquatic insects so that they are aware of the role these insects play in the aquatic habitats of my desert.  So, naturally, the subject of my educational display is aquatic insects.  Through experience, I’ve found that the best way to teach people about aquatic insects is to show them live insects.  Nothing draws attention to aquatics like a big dragonfly nymph squirting water out of its butt to move or a giant water bug devouring some helpless fish!  However, my display needed to be largely maintenance-free too and most aquatic insect displays are  anything but.  After brainstorming options for how I might balance maintenance requirements with a splashy educational experience, I decided to build a pond.  I used what I know about the habitat requirements of Sonoran Desert aquatic insects to design a pond that should attract a variety of aquatic insects so that they will find and colonize it themselves.  This way, Biosphere visitors will see live insects in a semi-natural habitat and the maintenance on the display should be minimal, fulfilling both of my goals for the project.

For the next few posts, I’m going to talk about my pond.  But first, a disclaimer!  I have never made a pond before.  I’ve read several books on the subject, so I had a good idea of what I was trying to do, but I’ve never actually made one.  Anyone who reads this series and wants to build their own insect pond (or simply a garden pond) should wait until I have a chance to make sure it’s being colonized by insects at the May Biosphere fellows meeting before following my example.  That said, I hope you find the idea intriguing and consider building your own pond for aquatic insects!

Next time I’ll cover choosing a site and container to hold the water, followed by a post on selecting substrates (the stuff on the bottom or sticking out of the pond that the insects use to hold onto or otherwise use to survive), including rocks and plants.  I’ll finish up the series by posting about the plumbing and electrical systems my pond required and suggest some ways to avoid turning a garden pond into a stagnant mosquito magnet.  Hope you enjoy the series!

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