Backyard Aquaponics
A place to discuss aquaponics

I've been reading here for a while, messing around with a small, solar powered NFT mini-system and have finally gotten the main pieces in place for my first flood/drain small system. Part of the goal of this is that I work with urban farming projects in Oakland/Berkeley, Ca, USA and I've been wanting a simple system to demonstrate to people the basic ideas of aquaponics. While the solar mini-system does that to a degree, it's a fifteen gallon tank with 30 gold fish. I wanted a simple, easy to understand, easy to replicate system that I could show to schools, friends and community gardens in the area to see who might be interested.

The basics of the system are a 100 gallon tub (4' x 3' x 2' tall) and three 27 gallon rubber maid totes filled with 1/4" lava rock. As you can see from the picture, even after a bunch of washing and rinsing, I didn't get all of the red dust off the lava rock, so I'm going to let the system cycle without fish for a while and see how much of it settles in the fish tank, settles in the grow beds or stays floating. The pump is a wayne, 1/2 hp, 1800 gph vortex pump, one that is supposedly good at sucking up solids up to 1/2". I'm thinking of the system as a 60 gallon fish tank with 30+ gallons of sump built into it. Right now, filling all three grow beds with water leaves the tank a bit under half way full. All the beds still need more lava rock (man the washing is taking a lot of work and not working as easily as I had hoped) and then I'll get the plants in. The bins are roughly 2.5' x 1.5' x 1.2', 3,6 cf each. I don't think I'm going to fill them up all the way, so I'll end up with about 60 gallons of grow beds, but they should be pretty heavily planted.

The bins I got at home depot, $12/each. The pump was $45 at Amazon, the tub $90 at a local pet store. I built the table for the bins out of scrap 2x4's and a half sheet of plywood. The pump takes a 3/4" hose fitting, which I bridged to 3/4" pvc, ran a pipe up to the T, 3/4" to the two beds facing the same direction and 1/2" to the bottom bed (to try to even out the flow). Right now I'm doing some fine tuning of how long the pump needs to stay on to fill the beds to 1" below the gravel surface and how big of a drain hole I need so that the beds drain fast enough to have some drying out time before the next cycle.

I'm more of a tech guy so I went for a digital timer to control the pump. It has 20 programs/day, each program can turn the outlet on for some pre-determined number of minutes. Right now three minutes on fills the beds to the overflow holes, but I was wondering about a few extra minutes of cycling to improve circulation and aeration. The beds drained in about ten minutes. RIght now I've got it set up so that the beds are over the fish tank and just drain straight down into it. I'm planning on raising catfish, so we'll see what I need to do to get some heat into the fish tank to help keep the water near 80 degrees.

Right now this system has no back up, no redundancy. It's a pretty straightforward single pump system that would need to be in a location where it can be monitored with some degree of regularity. The easiest upgrade I can think of is a second pump/second timer, so each pump takes turns. That would provide a layer of redundancy and probably keep the fish alive until I figured out the other pump wasn't working. How I'd know that, however, is something I'm still thinking about :-) Here in Oakland we haven't had a power outage in 20 years or do, so power issues aren't soemthign I have to worry about. Cheap electronics and flaky pumps, however, happen on occasion, so that's most of what I'm trying to make a plan for.

In terms of fish, I'm planning on raising channel catfish. As I said earlier, I'm think of this as a 60 gallon system, so I'm hoping to end up with something near 30 lbs. of fish. The extra water I'm hoping will help reduce temperature and other spikes and maintain enough water in the tub during a flood. As I get closer to 20-30 big fish, I'll probably have to add in a grow bed or two to help pull out the nitrogen. But I'm planning on some pretty dense planting of leafy greens that a group of ten families or so will be eating from, so hopefully I'll make up in plant activity what I don't quite have in grow bed volume. I've got all sorts of options of pulling out 20-30 gallons/week to water my blueberries and olalla berries (planted in the ground) and then just refill with fresh water. My water has chloramine so that would mean ongoing water treatment, which doesn't seem like the best idea. So I'm more thinking about adding in a few extra grow beds as the fish get bigger.

Other than that, I'm trying to keep it simple and overall, it's looking like something I could replicate pretty easily for not so much money. So far the total budget for everything but the fish is around $250.

Ok, here is a picture of the current state of the project, more to come as things develop, especially when I can finally get my fish :-)

p.s. and as with everyone it seems here, this project is the trial run for my bigger 600 gallon green house project I'll start working on once my corn is finally ready to eat and the last of my tomatoes and squash are done :-)

Hay there Rick, welcome!

Channel catifish. It is not mandatory to keep water at 80 F for channel catfish. Though they grow best with warm water, they still keep eating some even with water below 70 F.
I would highly recommend getting an air pump and a high quality big air stone. For a up to 100 gallon tank, look for something that can provide .3 cfm at 2 psi and an air stone that can handle that much air. That should give you way more than enough air for that one system. (for the planned big system, just figure you need 1 cfm of air for each 400 gallons of water and the pump needs to provide that much air at (1psi for the air stones + 1psi for each 28" of depth) and always give yourself a little extra just because.

If your pump is not running constantly to keep up the aeration, your channel catfish will not be happy without the air pump. They like good aeration.

As to how much fish your little system there can support...........
3 x 27 gallon totes would be 81 gallons but you said you won't be filling them up so you are figuring 60 gallons of grow bed.
5lb of fish per 25 gallons or grow bed is a good heavy max for a relatively new system.
or 1 lb of fish per 5 gallons of grow bed.
I wouldn't start out with more than 12 fish and that is if you plan on eating 1 lb catfish.

If you want to raise 30 lb of fish in that system, you will want 150 gallons of grow bed, and you will probably have to add some sort of sump (or extra attached tank) so you have a total of 150 gallons of water holding capacity for the system. 30 lb of catfish should be in at least 75 gallons of water but they will be a bit crowded in that.

Now you mention doing water changes and such but even if you do that, you will need enough filtration capacity to handle the solids and ammonia/nitrite conversion to keep the catfish healthy. They react very quickly to poor water quality and if you want to push the limits for stocking, minimal filtration, air and water quality, Catfish are not the best choice of fish. However, I don't know if you can legally do tilapia and they do require warm water.

Anyway, enough of the reality check.
What you have so far is looking pretty good. FYI, that pump, if you hook it to larger piping, it will deliver much better water flow and could handle a much bigger system. Just because a pump comes with a garden hose adapter doesn't mean it should be run that way very long. The adapter is really meant to make it easy for people to pump out their basements when there is a flood and still a larger discharge hose would be far more efficient.

Washing lava rock. Tedious and yes you will never rinse it enough so that it doesn't cloud the water at least a little bit. I find swishing a basket full of rock in a few bins or water (progressively cleaner each swish) seems to be pretty easy, effective, and more water efficient than hosing the media down. As the system cycles and starts building up some bio-slime, the water should clear. You can also add socks or nappies over the ends of the pipes where the water enters the grow beds to help catch some of the stuff for a while, just gotta change them every so often as they get clogged up.

Looking good, welcome aboard

Thanks a ton for all the good info and the reality check :-) Crazy busy couple of days at work coming up, but I'll be thinking through what you said and check in over the weekend

Reality checks are always good things, so no worries on helping me think realistically about this system, especially if this is a system I'd like to use as a demo.

Part of why I was thinking of catfish is because they can handle a wider range of termperatures and I don't have to heat the water constantly. I'll be curious to see what kind of water temp I can keep in the green house I'll be building and I have some options for solar water warming, but I'm counting on them sticking around if I can't keep the water hot enough. I'm curious, in your system, what temperature variation do you see from night to day?

So I get the push for more grow beds, but straight volume of grow bed isn't the only factor in a system's ability to process nitrogen. Different plants and different planting densities would have a lot to do with overall system capacity. One system with some tomatoes, lettuce and herbs vs. a system with a high density planting of corn will be able to process radically different amounts of nitrogen. One thing I'm curious to see is that plants also process significantly different amounts of nitrogen at different stages of growth. So do you time what plants are needing what in order to maximize nitrogen processing as the fish get larger (thereby increasing density?)

It seems that every system will have pretty different nitrogen processing requirements depending on how big the fish are. Let's say I wanted to shoot for 30 lbs. of fish in my 100 gallon tank, so maybe I get 45 fingerlings since some won't make it along the way. But 45 fingerlings won't produce that much nitrogen at all compared to what 30 fish close to 1 lb. each would produce. Over winter, while the fish are growing more slowly (depending on water temperature) I'm imagining nitrogen processing requirements are hugely reduced as well.

Do folks add and subtract grow beds to a system as the nitrogen processing requirements go up and down? It would seem like a fairly dynamic process, to monitor water quality and add or subtract grow beds as needed.

I hear the call for an air pump, I'll make sure to get something going when I get the fish here, and I hadn't thought about using 1.25" pipe coming out of the pump (that's its standard output size, it has a 3/4" adapter that I'm using right now). That would be great to boost the output of the pump a bunch, I'll give that a try tomorrow.

Thanks again for all the good info. I'll do some tinkering on my end, check how the red dust in the water is down, how much boost I get from some bigger pipe and think through a good way to be ready to add grow beds as needed.

Let's see:

temp variation (in my insulated box/growbed system) is about 1degF typ, 3degF max (say .5 to 1.5 degC).

You could use the same amt of growbeds and simply plant more or less. You may need to keep in mind that certain plants (like tomatoes) are real pigs for nitrates and may rob the others. I believe that as a system gets older and has more organic material in the growbeds it will tend to store nutrients better, thus flattening fluctuations. Meanwhile I add some nutrients as needed or simply plant more stuff as nitrates increase or as I expect them to. Since you can go really high on nitrates without trouble I try to stay between 40 and 400 ppm. If plants are yellowing from lack of nitrates, harvest what you can, cut back others, and fertilize. If all is going well and nitrates are going up high, plant more.

Keeping the same amt of growbeds may be excessive when you don't have many fish, so you could cut some off when you don't need them. This will help reduce temp fluctuations, but may increase chemistry fluctuations as old dead detached growbeds are first refilled and add their load of dead bacteria and other stuff to the fish water. Might be better to try to avoid this by simply not planting them when you don't need them, but keeping the water running at least once or twice a day.

Wow, really, only 1-3 degrees of temp change from day to night? That seems amazing for a tank in a green house that gets pretty toasty during the day. I get it's a lot of water and you do have it pretty shaded and insulated I guess as well, so what's the average temperature? Wouldn't normal lake temperatures change more than a few degrees from night to day or just in spots? I can't imagine the water at the bottom of a lake stays 80 degrees, or even 70, so catfish swim around a bunch I guess and find water that is the temperature they prefer?

avg sits at about 70degF these days, but has gotten as high as near 80degF. Had to keep 200watt heater in there for a couple months in winter to keep temp up to 60degF. Sorry, folks, too lazy to convert to degC. G'night.