Is there like a rule of thumb of the relation between the amount (and size) of fish and the amount of plants growing in a aquaponic system?

I started playing with aquaponics in a small setup, but I dont know if I have enough fish, or if they're big enough, I bought 10 goldfish, the kind they use as food for bigger fish, this is my tiny setup

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(Pic was taken before the fish where added, but they're there now. Click to enlarge.)

  • Just a note: feeder gold fish (which are usually Comet-tail goldfish) can grow to be about a foot long. They should be fine for now but unless you are thinking about increasing your reservoir size in the future they will quickly outgrow their container.
    – WienerDog
    Apr 12, 2012 at 14:48
  • yes, thank you, I wanted to get something done quickly and pay as little as possible, just to try it and learn. i'm currently researching more and figuring out what to do next, this time on a bigger scale.
    – geermc4
    Apr 12, 2012 at 17:13

1 Answer 1


As far as I can tell from being an aquarium enthusiast and a hydroponics enthusiast there is not a set in stone rule when it comes to this. The problem is that 2 different fish can produce different amounts of waste (goldfish are notorious for producing a lot of waste), and two different types of plants can have varying absorption rates.

However there are a few thing to go off of. Using testing kits (for Ammonia, nitrate, and nitrite) you can keep a chart of your levels every week and determine if you need more fish to make more waste, or less fish if you have too much waste. From what I could find in a stable aquaponics setup: ammonia levels should range from 0.25 to 2.0 ppm; nitrite levels should range from 0.25 to 1 ppm, and nitrate levels should range from 2 to 150 ppm. Aquaponics is considered a "newer science" so it may take a lot of personal balancing to get everything within the right levels as there isn't a "standard" on how to do it.

Unrelated side notes: Forgive me if I'm being a little nosy but a few things I've gathered from your picture:

Do you have a cover lid for your water reservoir? From my experience with hydroponics, you want to limit light as much as possible in your water. Algae grows wonderfully (and seemingly out of nowhere sometimes) under grow light and will deplete all the oxygen in your fish reservoir which is bad for your fish and your plants.

How close is your grow light to your plants? It may of been that you just moved it to take the picture, but you want your grow light to be as close as possible to your plants.

Do you have an aquarium or wet/dry filter handy? A simple filter like this provides additional aeration for your fish and your plants and also an area (specifically the mesh material that does the filtering) where ammonia converting bacteria can live and thrive. You need these bacteria to convert ammonia into nitrates and nitrites (which are what your plants need to grow).

Are you supplimenting with additional nutrients? Nitrate and Nitrite are great for boosting plant growth, but that is not all they need. Trace amounts of phosphorus, magnesium, iron and other nutrients are needed for plants to grow properly. You may be lucky and find that some of these actually occur in the fish food you are feeding your goldfish, and any uneaten food will get dissolved into the water supply.

I apologize ahead of time if any of this is overbearing, just want to be thorough. Please ignore any of these if they aren't applicable.

  • A quick answer to your questions (i know it's against forum rules so moderators forgive me) Seems like I need another tester (or hope the one i ordered has that, think i got just a pH tester) I don't have it covered, i'll take note and cover them today I dont have a grow light, i have that outside, not sure if I they get enough light though I thought that's what the rocks where for (filtering) I saw a post in aquaponics.net.au that talked about suplements, so i got what they listed there, seaweed extract, iron and ALROC mineral rock, duno if it's enough. thanks for your comments :)
    – geermc4
    Apr 12, 2012 at 17:10
  • Cool, i accidentally got the right tester
    – geermc4
    Apr 12, 2012 at 17:20
  • I made a separate question for the filter thing, so we dont switch the scope of this question.
    – geermc4
    Apr 12, 2012 at 17:25
  • I hope I wasn't too overbearing, I just got excited about an aquaponics question :-) If you are outside and your plants are in their recommended light zone (full, part-sun, shade) then you will be fine. I thought it was in a garage or basement based on the pictures but I should have asked.
    – WienerDog
    Apr 12, 2012 at 18:23
  • unsure if it's getting enough light actually, i'll look in to it, they probably only get like 4-5 hours of direct sun light
    – geermc4
    Apr 12, 2012 at 18:28

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