Another TCLynx Public Service Announcement. Or perhaps that should be Fish Service Announcement?
There is a common Aquaponic condition that causes many people to feel the urge to add more fish. This urge should be fought and quashed ruthlessly unless you actually don't have any fish at all.
Just because your system could possibly support a certain MAX amount of fish mass, does not mean that it needs that much. Especially any system that retains it's solids.
During initial cycle up, plants my show signs of deficiency but adding more fish won't fix that, you are just cycling up and the system has not yet gained enough maturity to provide all that the plants need. You will just have to be patient, adding more fish won't speed the process, it generally takes as long as it takes and extra fiddling is more likely to slow things down than speed them up.
Once a system has a little maturity, it can easily keep plants happy with a minimal amount of fish or even run fishless for a while after a heavy fish load is removed.
The more fish you have, the faster things will wrong if anything negative happens. The less fish you have, the more leeway you get if the power goes out or the air pump quits or whatever.
I've never had any of my systems after they were cycled up reach 0 nitrates and I've run systems for weeks and even months without fish. When I have fish I often have a heavy load in the system and therefore, the solids in the grow beds can slowly break down for a long time and will keep the plants happy for ages even fishless. Don't assume your plants are suffering from lack of fish unless your nitrates are reading 0 and the older/lower leaves of the plants are yellowing. (Newer leaves yellowing with green veins is a sign of Iron deficiency, not a lack of nutrients.) I know of many people running systems that have never managed to measure nitrates but as long as the plants are happy, then there are enough fish.
Keep in mind that there are many other things that will make plants unhappy including too much nutrients, too much salt, too much or too little light, too wet around the crown (flooding too deep) or drying out (not flooding deep enough or not flooding at all) lack of or locked out iron because of pH, too high a pH, and many more.
So please stock systems appropriately. Recommended stocking levels would be like 20-25 small fish per 500 liters of flood and drain grow bed (assuming you will harvest them at 500 grams) or 1 fish per cubic foot of flood and drain grow bed (a cubic food is about 7.5 gallons and this is assuming a grow out size of 1 lb so if you are growing channel catfish, make it 1 fish per 2 cubic feet of grow bed.)
Now if you are just starting up a new system and it isn't cycled yet, (Fishless cycling might be a good idea) then you might only want to stock half the recommended level of fish for cycling up with fish.
It is OK to stock less than the recommended numbers!
Now I know many people growing tilapia get away with not following the above guidelines since tilapia seem to survive all sorts of toxic situations with minimal harm but it is still possible to have a fish kill with tilapia if something goes wrong and minimal stocking can work just fine with tilapia too.
Don't be afraid to allow your fish some space. I know those little fingerlings seem so small in a big tank but they will grow, they appreciate the space.