Backyard Aquaponics
A place to discuss aquaponics

Clutching at straws now

Tim et al -
The issue that you may have with the shallow ponds is evaporation and temperature fluctuation. Since more water is on the surface, you have a large solar collector (warm water, DO drops), you have more oxygen exchange, but not much way to stir up the water.
Also, with the decreased depth, you will have less thermal stability. Evaporation will play a bigger role. If you lose 10cm of water out of a 1m pool, it's no big deal; but if you lose 10cm out of 15cm, you are in real trouble, and the fish are too.

I guess I am spoiled. I know much of Australia has severe water restrictions, etc, but to me, with 160-80 inches of rain a year and an ever flowing spring and a nice river, a bit of water loss in a closed system is not such a big deal. Evaporated wated can merely be replaced. The evaporation doesn't take any of the fish manure with it... so...

Tim B, heating is not really an issue here, as you thought. Its one of the things I love about people from FNQ, you have it like we do: hot, humid, etc, and all of the benefits and problems of lowland humid tropical life are familiar to all of us.

I think the water transfer to the top of the grow bed and then out the bottom into the fish tank/pond would aerate and oxygenate the water sufficiently, even with a shallow tank. Maybe I am missing something?

JT,

I found more on the Water Motor. It was made at Campo Neuvo in Bolivia:
Home Power Amagazine Article on Water Motor

This is the pdf of the original article I read. I hope you can use it!

C

Greenedo true evap is a problem i moniter daily a float valve wouldnt be hard to hook up.Also whta ive done with my test pond is the width is just the right size for styrofoam boxes which otherwise go to the dump. i cut them up and float on the surface of the pond taking some out as i expand my plantings, This goes a long way towars keeping the temp down and the crays love the cover. Oh and i cut small styro squares 4-5 and hot melt them to the styro covers so they sit a couple of centimeters above the water surface that way i dont significantly reduce my surface area.

Tim B, that is a brilliant solution!

Sounds great, but if you're covering the surface, wouldn't that also cut down on O2 exchange? Even sitting above the water, you're holding stagnant air.
If the fishies keep the surface stirred, then you have your pump to keep the water moving and the O2 dissolved.
Anyway, can't argue with success, that is, unless you're in politics.

Well, my understanding is that with the pumping of the water through the grow beds, and the reentry of the water into the fish container (pond/tank), the water would be oxygenated.

I see several ideas on these boards that are a fairly radical departure from the AP I was introduced to by Joels brilliant book and CD/DVD, so I am trying to get up to speed, but the system, or its variants, comprised of a closed loop between fish pond/tank and grow bed seems pretty perfect to me. I think such a design would keep oxygen levels high, and the addition of floating stuff would help reduce evaporation.

Chris- one of the draws of this site is that there are people trying many different things. If there were only one way to do AP, then the threads would run something like:
"How do I..."
"Read the book, it's all in there."
"But if I ..."
"It won't work, do it this way."
And we would miss out on all this speculation, experimentation, etc.
Joel and others have done phenomenal things, and have determined ways that work; but the book is not closed. Different people have different goals, different resources, and different areas of expertise.
When I started my thread on my proposed system, I had done a lot of research, and had my idea of what to do. Since then, I have made several revisions as I am trying to gather materials, and have gleaned other things from members that have altered my plans multiple times.
How will my system look when it is actually built? I'm not sure. But vetting it through the combined experience of this site, and members telling me, "Have you thought about...." will make the system better than when I originally proposed it.

Greenedo, your not wrong, when I first found out about the book and the forum i went hell for leather and built a small test system to find out how things would go.
Recently I haven`t paid it to much attention as I`m sourcing materials to build a bigger/better one as I now have more knowledge through here!

I wasn't meaning to say anything against anything. I have been pretty calcified by my limited exposure to ideas, truly! I see some possibilities put forth here that I have not considered, for example, somf of which looks promising, and some that look to me like they simply won't work.

My point above was that in any system with recirculating water, loss of oxygen shouldn't be a problem because in an AP system that has recirculating water, aeration is easily designed into the recirculation. That is part of the beauty of Joels system.

It is not so simple with Dissolved Oxygen (DO) .

Most commercial operations need to use pure oxygen injection to provide for their high stocking densities.

The higher the temperature of the water, then the less DO for the fish.

Algae create DO during the day and use DO at night.

DO value dives after a feeding.

A biofilter requires and consumes DO. The grow beds use DO.

With low stocking densities, there is less critical requirements on DO.

I start in the spring. I will use low stocking density and work up with experience. I also decided to invest in a DO meter for $230US.

I think it is important to maximize the DO from any reasonable (low cost) process possible in my system. Certainly, spraying or waterfalling the water helps. I also will run several air stones. Adding pure oxygen is too expensive and complicated.

Decaying organic matter will pull a lot of DO out of the water as it oxidizes. So, over feeding can crash the DO.

So many ways to run into trouble

Unless the tank is closed, I can't see that adding pure O2 is going to do much. The amount of DO is controlled by the partial pressure of O2 around, and if the top of the tank is open, it seems to me that you're just going to bleed O2 out there. In a sealed container pure O2 will give more DO.

Christopher- I haven't seen any system suffer from too much oxygen. Doug B probably has more practical experience that I, and the shallow ponds with the floating beds suspended over them shouldn't be that bad. I just got a little worried between this thread on solar powered/low/no powered, and other threads that have been rather active, on low-power systems, I was concerned that you would try to use the shallow ponds as your primary O2 exchange. If you have the pumps going, then you may be fine, but shallow ponds by themselves lead to heat, evaporation, and lower DO. When you cover them with Styrofoam, you reduce the heat, and possibly the evaporation, but you would also risk cutting down the O2 exchange.
I'm not knocking the idea, I just don't want you to try something, and come back with one of those "Oh, NO!" moments. I figure it's easier to change designs before building than after.

You will learn to watch the fish for clues on both water quality and DO. I kept standard aquariums for years, and the fish tell you a lot by their behavior. Gulping at the surface (when not begging for food--DO problem. Hiding -- maybe sick or injured or just new environment. Sulking or not eating well--check the water quality. btw, even just a bit of a ripple in the water surface, or a plunge of water into the tank can do good things for DO.

Do the math as best you can, and watch the fish.