Backyard Aquaponics
A place to discuss aquaponics

Hi Everyone,

Ive been planning this project since last fall when everthing in my small greenhouse died, Lol.

I think that i just about gotit figured out, i was going to set up a raft growbed system considting of two grow beds and one fish tank of all identical containers with the fish tank on the bottom. I was considering small 45 gal kids swimming pools about 9 inches deep 40 inches in diameter. My only problem is that im cheap and dont really want to have to run much more on electricity them a small pond pump. I was planning aeration of the water for the fish and for the roots by the waterfall method where oxygenation is achived by having a stream of water injected directly into the top grow bed cause the aeration.

My question is would this work? I have done alot of research online about raft hydroponic systems and they all use air stones for aeration.

like i said im cheap, so i was also thinking of eventually going completely of the grid. Solar cell powered pump would take up to much space in order to have a pump that would have enough capacity. I think a small pico turbine made from a small bucket would give enough pumping capacity to run my system only problem is how long would the fish live without water aeration?

Also where would the best place to put a sump in my system?



Total sytem footprit 4sqft

Welcome aboard, Grayman!

Sorry about your climate up there. Hey, you only have another month of miserable, then a month of chilly, then it should get nice. *grin*

I've always done flood/drain systems, but others can advise on raft systems. On the other hand, I can testify that AP is great: not only are the plants large and productive, but there are no gophers sucking the plants into the ground. Little demons.

If doing a raft system, you need to provide some means of solids filtration and perhaps some extra biofiltration beyond what the raft beds can provide.

As to pumping and aeration. How long would fish survive without aeration will depend much on the fish load, water temperatures, feed rates etc. I know of goldfish that survived all winter under snow and ice with no pumping and then other years they all die.

With minimal pumping and minimal aeration, you may only be able to grow minimal fish and plants. If limiting the electrical consumption of the system is your primary goal, then you design your system around the elements that use the electricity and resign yourself to a system with limited production. I'm not going to tell you that you can run a 5000 liter system on 45 watts for 15 minutes and hour during daylight hours only and still get 100 kg of fish out a season and 500 kg of produce.

The basic design numbers most of us here know best is the
3 kg of fish per 100 liters of flood and drain media filled grow bed with 50-100 liters of fish tank plus sump tank if needed.
Along with that we usually add that the volume of the fish tank should be turned over each hour if stocked anywhere near 3 kg of fish per 100 liters of grow bed and supplemental aeration may be needed, especially if the water pump isn't running constantly.

Now raft culture is different from flood and drain media in that there is no flood and drain action to provide aeration to the plant roots, bio filter bacteria, and other bacteria, all these things can quickly deplete dissolved oxygen quickly especially at night when plants are using oxygen and giving off carbon dioxide. Also the rafts on the surface of the water remove the primary way water can passively get aeration directly from the surface contact with the air.

Injecting water into the bottom of the raft tanks from the pump in the fish tank probably won't provide much aeration to the plants and I think you will find you need filtration before the water goes to the plants or the gunk build up around the plant roots will compound your aeration problems and could even go as far as causing root rot and anaerobic smelly situations in the raft beds.

You might be better off setting up something like a bakki shower to filter and aerate the water on it's way down to the raft beds instead but a bakki shower requires a fairly high flow rate or it become simply a trickle tower. Perhaps a trickle tower would work for your situation but I don't really know as I've not tried such a system myself.

I'm off grid now and have a 20 gallon FT, about to increase 2x or 3x but power consumption is very low. The air pump uses 4 watts and is on continuously. The pump is 9 watts and runs 15 min/hour. A digital timer from home depot controls the pump.

This has been fine but we woke up to no power this morning. We've had 4 cloudy days in a row, plus the kids have been home on vacation all week, and we haven't run the generator for a few days. It adds up. We shouldn't see that again till school lets out for the year.

On the plus side, the timer maintained all its settings.

BTW, the consensus seems to be that a 12v pump isn't worth it. Better to get a 120v with a small inverter battery setup. You could run your air pump and timer thru that no problem.

Thanks to everyone for repling

Perhaps i wasnt clear enough about the aeration method i wasnt going to inject the water back under the rafts but from above the surface of the water similar to the way water enters the flushbox on your toilet. Having said that do you think that a system of water cascading over obstacles would be better than the "toilet method" i described, lol.

As for going off the grid i didn't mean that my house would be off the grid i just want my greenhouse to be self sufficent. I was going to make a small vertical turbine directly drive a small pump. I was thinking about a couple of those small pumps that would ordinarly be driven by a electrical hand drill.

Thanks for the feedback guys sorry i wasn't clearer about my plans. Now that i have hopefully cleared up my master plan please give so additional feedback. yhinking about your initial feedback i think i may change my plan a little. Also i need to look into this biofiltration that you speak of. What do you think would be the best way to provide sufficent biofiltration.

Thanks again

Craig

Most of us here do flood and drain gravel beds (or other media) that act not only as a place to grow the plants but they are also the bio filters and solids filters and they in themselves don't require additional aeration the way many bio-filters and raft beds do. Gravel beds are also very low maintenance since you don't have to remove solids, clean or back flush filters ever day or anything like that. With media filled flood and drain systems you only need to worry about enough flow to keep the water quality good and enough supplemental aeration to keep the fish happy since the flood and drain action ensures the bacteria and plants always have enough air.

Read the useful information section and basic information section and they should help with much of the design numbers and there are some threads that might give you some ideas.

Hi, some thing I was going to try was a flood and drain in my raft system, it wont drain all the way just say 100mm or so, I was thinking a bell siphon with a air hole set down the side of it.
I have found good water flow and air is very important, my first lot of plants were stunted in growth

Thanks for the excelent idea one of the reasons that i was going to go with the raft system was the limited size of my fish tank this will solve the problem. Good insight, thanks.