Argh, I just wrote a whole answer to all the questions here and glitch, lost it all
My Blog on some of this subject
on BYAP I usually recommend reading the Basic Info Section and Useful Info section then choose a couple of the longer member system threads to read all the way through (keep a scratch paper by the computer to track which page you left off at so you can pick it up again later since it will probably take you more than one sitting.)
1-yes, having at least as much media bed as you have fish tank volume is a good idea for a simple system.
2-CHOP stands for Constant Height One Pump, meaning Constant water Height In Fish Tank, Pump In Sump Tank which is also known as CHIFT PIST and yes that is for a flood and drain system.
3-Yes 12 inches deep is a really good depth for flood and drain grow beds. It allows for a top dry layer (plants don't like when the top of the media gets wet too much) and it also allows for a bottom layer that may never drain especially in a siphon system while still allowing a good middle layer of actual flood and drain media. 12 inches doesn't seem deep to me, I've got lots of 24 inch deep grow beds. (I understand that you might not want to go that deep for a little aquarium system and if you are only growing small plants you can manage a shallower bed on a timed flood and drain aquarium system indoors.)
4-Swirl filters are for systems that don't use media beds like NFT or DWC raft systems where they need to remove the solids to keep them from gunking up the plant roots. In media bed systems where there is not enough grow beds for the system, a swirl filter might also be used but is not necessary in a system that is designed with enough media bed for the size fish tank and fish load.
5-I'm not sure how to recommend stocking density for something like this. You might want to look to aquarium guidelines for this. I'm used to making recommendations for systems with fish growing out to a pound or more which is not appropriate to a 20 gallon tank.
6-Depends on the design of the system. In a simple 20 gallon fish tank pumping to a 20 gallon grow bed flooding and draining back to the fish tank, It would be 20 gallons and the fish tank level would fluctuate by about 6-10 gallons.
Finally, I answered that first.
That's a great idea, small systems can be very rewarding and good for quick learning. You can grow interesting plants with a 20 gallon aquarium setup. Here are a couple that I've done with small aquaria, maybe spark some ideas for you:
1. For fullest stocking you should have 2:1 growbed to fish tank volume. Most folks do not reach this, instead 1:1 or 1.5:1.
2. CHOP stands for constant heigh one pump, originally called CHIFT PIST on the BYAP forum, which stands for constant height in fish tank pump in sump tank. They can be flood and drain, just pump with a timer or put a siphon on the beds.
3. 1 foot is good for anything larger than a wee plant. If you want to grow tomatoes or broccoli or anything significant you should have at least this depth.
4. Swirl filters are not necessary unless you don't have enough grow bed volume for the fish load. Plan for enough grow beds and you won't need one.
5. Someone else can mention the ratios, I have about five mixed size goldfish and koi in my 20 gallon aquarium.
6. As much as you can fit, if you can have a sump that will help. The issue is that if you flood and drain the bed then the tank will get very low.
These plants are growing from the 20 gallon aquarium with the 5 fish in it:
Thanks for all the answers.
As for the grow beds and plants. This small system will likely have just salad greens in the grow bed. I can't really start until I get the shed built, I just don't have the space to work on a system right now. One idea I've had for this is to learn about it and have this system running in the house over next Winter. Do the systems smell? I'll have it in the basement, but if it stinks it would be a hard sell.
Dave, a couple questions about your small systems. Those plenum spacers, do they just give you support for a false bottom under the grow bed? And that would be a continuous flow system? Are there just some holes on the bottom of that PVC pipe on top of the GB? The pump continuously pumps water out of the grow bed and into the fish tank? Would you happen to have a link that describes how that water bridge works? In the diagram, I don't quite get it.
THe plants in the previous picture come from a system like this, which I call a Rendezvous system. The plants are in sub-irrigated planters and are rotated into the system for 12 hours once per week to be watered and to remove solids from the aquarium (the timing is not in stone). I have a nice collection of plants from this which were started around the beginning of this year. I like this setup because the plants can be located anywhere, they are not tethered to a grow bed for instance.