Backyard Aquaponics
A place to discuss aquaponics

A friend wants to try aquaponic in her kitchen to try grow mainly herbs. She is a total newbie when it comes to aquarium and aquaponic. A 20g tank (24" x 13" x 17"h) is probably friendlier space wise as it will sit on her kitchen counter top.

How about:
-bunch of tetras as fish in that 20g tank,
-some sort of dwc floating on top;
-a pumped sponge in tank filter to pump the water to trays with media then return to tank via gravity?
-she has a 6ft window so space enough for say 2 small trays to sit on the windowsill.

Not sure if say 20-30 small tetras can produce enough to feed plants with grow surface 2 to 3 times the surface of that tank? She wants to grow Parsley, Cilantro, thyme, green onion, basil, chilly pepper etc., whatever fits the space.

She won't mind to have more trays for more herbs if the fishes can support them. But she would like to minimize having to regularly change water, ideally only add water, feed fishes, and trim herbs.

Thoughts?

You wont need many fish to produce a lot of plant growth.
I have 8 small trout 3-4 1/2" long and feed them 1/2 a teaspoon twice a day and they support 61 square feet of grow bed with ideal chemistry (See pic).

Pete.

Looks like a 10g aquarium with 10 tetras may be more than enough for her, less fish less need for water change etc

I've never done a tiny system but thought about it many times.
From what I've read about around here I believe due to the small volume there will be challenges in maintaining the water chemistry. Larger capacity systems have the luxury of slower rates of change which gives us a better chance of fixing and or altering something before it snowballs out of control.

When beginning the environment for both the fish and the plants are not ideal however the plants will tolerate a wider variety of climates than the fish.

I'd suggest setting it up and running fishless until the plants have established themselves to seedling size. Use a couple of caps of Seasol Power Feed mixed with a gallon of system water sprinkled over the media as a substitute for fish. This mixture will last a couple of months in a small system in which time you should be monitoring with an API test kit. Essentially it becomes a hydroponic system in preparation for fish. Once the system water stabalizes you should consider what type and how many fish you'd need.

Pete.