Backyard Aquaponics
A place to discuss aquaponics

I think the consensus seems to be it's more efficient to get an AC pump & an inverter to run off the battery. It's one of my upcoming projects.

I'll wade in on the fish choice topic a little here. First I'm in Central Florida which is supposedly almost sub-tropical (well so much for global warming, we have had freezes each winter since I started doing aquaponics.)

My First year I started with channel catfish and we added tilapia.
Catfish can survive cold and don't quit eating till the water gets down into the low 50's F.
Tilapia only survive down to the low 50's F and they don't really eat or grow below 70 F.

I started out with a greenhouse for my first two winters, just a plastic film, no double wall insulation or anything fancy but this is Florida so I didn't think I needed it. Well two winters in a row my water in the greenhouse got cold enough to kill tilapia if I didn't run hot water from the hot water heater into it. I suppose I could have just dummped a large amount of the aquaponic water and just pumped in the well water at 70 F to keep things warm enough but that would have wasted a lot of water.

Anyway, I had some solar heating going but it takes a lot to keep a system with around 1000 gallons of water warm and the days are shorter and sometimes cloudier.

Most of my heating came from keeping the greenhouse closed up during the day to regain some heat. This actually made most of my plants fairly unhappy. The tropical stuff survived but was kinda dormant through it so not that big a deal. The cool weather crops suffered from the heat in the day and in the greenhouse tended to get attacked by aphids and there are not as many predators in the greenhouse to protect my plants. The warm weather crops survived but didn't thrive with the extreme temperature fluctuations and reduced air flow from keeping the greenhouse closed up. Spider mites attacked the tomatoes every winter and the only reason it wasn't that big a problem that the plants did so poorly was that the water was cool enough that the fish were not eating that much and the nitrates were not too high.

So I'm taking it as a blessing that I had to take down the greenhouse (non-permitted structure) and I no longer try to keep the water warm for tilapia. I'm sticking with the Channel Catfish which can survive the cold (as long as you don't over feed them during it.) We have actually found that the channel catfish in our situation grow more quickly than the tilapia, we like the taste as well as or better and they are easier to clean (choice clean 1, 5 pound catfish or 10, 8 oz tilapia?) Only drawback is I have to get fingerlings each year but that is really fairly easy and not costly, if one had a natural pond, one might be able to leave a few big catfish in it and arrange for breeding at home. My cool weather veggies are doing so much better this year in the exposed systems. Granted this winter has been a bit more mild than previous years.

Something to keep in mind. Even if you sink your fish tank in the ground, flood and drain grow beds are going to be extremely good heat exchangers at bringing your water temperature closer to whatever the air temperature is. The geo-exchange with the ground may help but only so much. When really extreme weather is expected, I now switch my smaller system to constant flood to retain a bit more stability.

Thanks everyone for the great ideas! You got my mind thinking about different experiments!

merkurmaniac: DC pumps are basically only available for industrial applications. The common person won't ever need a DC pump because we like to just plug things into our walls and have it just work So, you don't see DC pumps in retail stores..... having said that, there is a market for marine pumps because when you're on a boat, you don't have a wall to plug your pump into. Stay away from those, they aren't make for efficiency. However they are nice to have when you need to pump water in some remote location. They are typically 12v, what I am shooting for is 24v-48v.. these are for more serious applications.

Cycleponics?
What if one rode a bike and filled up a storage tank that then trickled into the growbeds throughout the day, and then perhaps pumped it up again for the night? The storage tank would have a regulator on it so it doesn't dump it's load quickly, and then the growbed just dumps back into the fishtank.

Many of these ideas have been discussed (header tanks to be filled by wind or solar or human power) to trickle through the day. They would require very low stocking density so that the fish wouldn't run out of dissolved oxygen because of only a small amount of water flow.
In more standard applications we say the minimum amount of flow per hour needs to be equal to the fish tank volume. In my systems I actually move probably 3-4 times my fish tank volume each hour. You are not likely to manage this by filling a header tank once per day so you are not going to be able to stock very many fish.

I have to respectfully disagree here. The thing is, DC applications are still on the "bleeding edge" if you will. For generations we have molded our lifestyles around AC for various reasons such as long distance transmission issues. Up until now, people were bound to the grid if they wanted to live a modern life of electronically convenience. Now we have more and more tools to generate our own energy at affordable costs, there will soon be a DC appliance revolution to ensue. Technology, prices, and efficiency will only get better and better from here.

So DC pumps aren't very popular on the consumer market because 99.9% of people have an outlet on a wall that they prefer to plug things into. That's one reason, but another is that up until recently, DC motors weren't incredibly efficient. They used brushed motors that have short lifespans (and/or maintenance), but now brushless motors have gone mainstream over the past 10 years. I remember when we were flying electric airplanes and the brushless motor meant a lot -- more power & more battery life (flight time). They were so expensive back then, but now days they are extremely affordable. Brushless motors have major advantages, such as the overall lifetime is comparable to AC motors. The reason I'm explaining all these is because with the adoption of brushless technology, DC pumps are bound to become better and better.

With the inverter situation, I don't seen why you wouldn't consider using DC pumps. I know that it seems like DC motors are overpriced, but you gotta consider how much you have to spend to get a decent inverter. By nature inverters have energy loss, so that is something to consider too. Even if a DC and AC pump were considered equal, I'd count out the AC pump if the system was not grid-tied because of the 10-15% inverter loss. This is the reason modern off-the-grid houses are outfitted with DC lights and refrigerators, to cut the inverter out of the picture for every day uses.



You're definitely right. You wouldn't be able to keep a dense stock off fish, but for a backyard system, that is OK. You could add an air-stone though. I might develop an experiment for this in the future. I think it would be interesting to deploy in nations that don't have access to stable electrify, but the concept/model has to be matured first. An interesting idea would be to have the bicycle system as a backup or supplementary to a low-cost solar setup. One of my solar-pumps still cycles water even when it's cloudy, but not very much... A quick run on the bicycle can solve that problem.

Well, the water in the FT is supposed to cycle once per hour. That's be a pretty big commitment to ride a bike 15"/hour.

If you are seriously considering using a bicycle, but out the battery, the inverter and the pump. Have the bicycle turn the pump directly. I have always thought that it would be cool to have a gym where each exercise you do lifts or pumps colored water that would generate electricity as it fell. Kind of a "keep moving to keep the lights on" type of deal.

If you had the storage tank, i'd work towards a way to lift the water right up to it while getting exercise. The right pump might bolt right up to the crank or be spun off the tire.

Not practical long term at all, but it might be fun to try and keep up, expecially if you needed the exercise anyways.

lynx: were you able to feed Tilapia grass clippings, or is that fantasy ? I may have to rethink them.

I've looked at the mechanical pumps before.. Very neat. They have a shaft that you can hook up to a cordless drill. It would be easy to hook the bike up after a little welding.

Awesome thread,

I have considered a lot of these questions lately too.

bio gas generation (takes kitchen scraps as input, and outputs methane gas for heat, electricity), this could supplement a solar heating setup during the winter.

homemade fish food (3reef.com has a great forum, and when i googled homemade fish food a few recipes came up, but it gives you the idea of how to start making your own at home with leftover kitchen scraps....also if you google fish pellet food and then google i think it's xtreme fish pellet food....xtreme is the company name and is spelled correctly...you can read the ingredient list to also get an idea of what to put into fish food)

cool weather crops for winter (i recently read a book by Eliot Coleman who lives in Maine and uses deep organic techniques and unheated greenhouses (some mobile) to grow produce 365 days / year!) fascinating reading, not sure where it's applicable to aquaponics, but might help you.

I found aquaponics, in my search for sustainable food systems.

hope to hear more from you, how are things going there?


take care,

jeff c

Like the thread... good to have a place to kick around ideas like these

have you checked out the Duckweed thread? I think its the one that talks about a turnkey unit that produces its own power and heat in a geodesic dome from burning duckweed in a Biomass Generator.

Love the concept of that and would like to set-up a test system one day... started doing some research on how to build a Biomass Generator... still a long way to go before ive got my head around the whole system tho... ie: using heat from the Gen to dry the duckweed, etc...

Hello,

I use a DC pump for my small indoor setup. It is a PC cooling pump, and is 12 volts. Specifically I use the Danger Den DD-CPX Pro. It is rated at around 18 watts and can move around 800 liters per hour. The rated voltage is 10.8 - 13.2 Volts DC. I have run it from a battery, directly from a solar panel, and now I am currently using a PC power supply. These pumps have to be primed and do not like air bubbles in the line. Also, these pumps are not submersible.