Filtering Fish Solids Vs. Worm Digestion in the System

Roughly 100 gallon system using either goldfish (a couple hundred) or perch (likely 50 or so). I'm debating whether to let the solids collect in a conversion bed and let worms eat it or to filter it out and then add it back in. What are your thoughts? Thank you in advance.

It depends...

Do you want to use the fish fertilizer somewhere else?

I try to filter out as much solids as practical.   There is a lot of information on re-mineralization tanks,  this may be and good intermediate option for you.   At that density it sounds like you have a really good way of oxygenating your system.   Good luck

I use worms in my grow beds as well as a radial filter before the beds to filter out a lot of the solids. The worms do a great job breaking down the solids but they do have castings that will accumulate in your system. I've just set up a second filter to catch the castings as they leave the sump.  Otherwise they'll keep circulating in your system until they find a place to settle. They were building up in my raft bed. Now I have to figure out a way to separate the castings from the filter and use them in my garden. Probably another radial or swirl filter from the sump.

I very little practical experience with keeping fish, but my gut feeling is that a healthy nutrient cycle needs not only animals (fish and worms) but also plants. And if nutrients are added into the system in the form of fish feed or anything, some nutrients might need to be removed from the cycle, for example by irrigating plants that won't go back into the system, or harvesting fish or plant products (or worms) out of it.

If you are really going to have that many fish in the system you are most certainly going to want to have some form of solids removal.... or a TON of grow bed space. Usually a good standard is to have 1 to 2 pounds of fish for every five gallons. Each goldfish will get up to a pound. Just some FYI


The best way to calculate the amount of fish to get is first figure out how many plants you aim to grow. For every square meter of plants you plant to grow you will need to feed about 60 to 100 mg of feed per day in order to not add supplements in the form of kelp extracts and whatnot. If you are fine with adding a little bit of supplements you can go all the way down to 13mg of feed a day and still have enough nitrates for the square meter of plants and be able to grow. Just add some supplements once a month or so.

In my 150gal system I have 13 goldfish, 2 koi, and 1 butterfly koi. They may be too much as they get bigger. I can sell them to my local pet shop (at a massive profit on the koi) and use the money to buy more feed.

I only have flood/drain gravel beds. No filtration otherwise. Would add filtration to a DWC if added later on. Just worms in the beds.

The bonus of gravel beds is their innate ability to mineralize EVERYTHING. So you can often get away with the 13mg rate in a gravel system with NO SUPPLIMENTs once the system matures after 6 - 12 months.

Check out the "aquaponics god" and "bright agrotech" video channels on YouTube. They have great info. on this kind of thing.

Here is a link to my series I am starting on my system...

Marty