Backyard Aquaponics
A place to discuss aquaponics

I have been noticing some broccoli plants with leaves eaten, look every time and found no critters. As time passes, I see more and more leaves eaten. Looking under several leaves, still not seeing anything. Now my bell peppers are getting eaten, still finding no suspect.
Today I called from reinforcements, my kids. I offered $5 bucks to the first one to find the caterpillar who has been eating my plants.
Well low and behold, I have been looking for one big one. Come to find out, there are about 60 little once. I have an enclosed greenhouse, puzzled how they all got in there, but they are there.
I read on here that Dippel dust or Thuricide is effective for treatment, and wont hurt the fish. Has anyone ever used them? Is it a dust or a spray?
I have NEVER used any pesticide, and am very nervous. Any advice would be very much appreciated. I have included a pic of the critters. The pic is using a magnifying lens, they are tiny in real life.
I have a ebb and flow bed with hydroton as a media.

Dipel is a powder which you mix with water to activate the bacteria, Bacillus thuringiensis, (Bt). The caterpillars eat it and die a few days later, it stops them eating. It is only effective against butterfly and moth caterpillars, and has no withholding period, so you can eat vegies that have been recently sprayed with it. It's best to spray tops and bottoms of leaves, to maximise the amount the caterpillar ingests..