Backyard Aquaponics
A place to discuss aquaponics

How many fish?
How much do you feed them and how often?
What are the other reading..ph, amonia and nitrite?

about 60 small goldfish...6-13cm
4-5 tablespoons of grobest floating pellets each morning.
ph about 7, no other test available unfortunately.

It's fish mass is 3-4 times more than I had before...but I guess my growbed area has almost quadrupled....the plant load is light though...it's not packed in there. I could easily fit in more fish.

I'm not the best person to give advise, but my system is smaller then yours. I have 39 fish in it and I feed them 5 or 6 times a day. They get a small handful each time - maybe 2 table spoons. The plant growth is amazing. You might just be underfeeding. I have bluegill and tilapia, and they stop eating when full and the remains just float around until getting flushed to the growbeds. I have been able to dial in the feeding such that it all gets eaten. I also have quite a bit of shade over the plants...they mostly get ambient light for the most part of the day.

I also have a radhish that has not grown from day one. I transplanted it from the garden - I assume it was stunted in the garden and just stopped growing - it is now very shaded by other plants. Another radish transplanted at the same time went straight to bolting and is 2-3 feet tall so I do not think it is the light. So the other thing is it could just be the plants....so if you have the space maybe try some new ones and see what happens.

Can anyone else speculate on his poor plant growth?

speculate - too much sodium from sodium bicarbonate buffering or salt?