Recommended Stocking Levels vs Max Stocking Levels

Originally posted by TCLynx on AGC on May 29, 2010

It has been brought to my attention that quoting the “max stocking levels” with system design information might be counterproductive with many people new to Aquaponics. It seems that many people take this number and figure it is standard and that they should stock their systems accordingly even when brand new.

I agree and I now see better why I’m then constantly reminding people “no-no that is the max, you should start with less than that!”

There is one well known aquaponics shop that generally gives stocking recommendations that would put the grown out total fish weight at about 2 kg per 100 liters of flood and drain grow bed (rather than the max which is 3 kg per 100 liters of flood and drain grow bed.) I think this is very reasonable advise.

I’m not quite sure how best to round that out in imperial measure that will be appropriate and still easy to remember and do math with. One pound of fish per cubic foot of flood and drain media seems like a fairly easy thing to remember and is an even lower stocking density than 2 kg per 100 liters.

As has been noted by people with much experience selling aquaponics systems and explaining aquaponics to people all day every day, the people who are prepared to handle max stocking density don’t really need to be told how many fish they can support and the people who do need to be told, should not be stocking anywhere near the max!!!!

A flood and drain media based aquaponics system does not require max fish stocking to get good plant growth.

So I am going to be changing my standard answer about how much fish a system can support to recommending that people stock at a recommended stocking level.
2 kg per 100 liters of flood and drain media filled grow bed
or
1 lb of fish per cubic foot of flood and drain media filled grow bed

(a cubic foot would hold about 7.5 liquid gallons.)

to figure that into a number of fish to start stocking with….
that might be 4 fish per 100 liters (assuming you will harvest fish at 500 grams)
or
1 fish per cubic foot. (assuming harvest at 1lb)

Might seem like a small amount of fish at the start but when cycling up a new system, ya gotta start slow and high quality feed for fingerlings can provide a good amount of nutrient once the system is cycled up.

If growing something like catfish, I would recommend planning the numbers a little different. Figure the fish will get to two pounds at least unless the fish tank is small. Catfish are just fine to eat small but they are also easily grown much larger so one might stock initially at 1 fish per 2 cubic feet of grow bed and then start eating some fish while they are smaller so that there will be enough space/filtration to grow some of the catfish larger as the numbers of fish are reduced.

Once a person gains more experience with aquaponics and fish keeping, they can figure out their own stocking levels for their systems.