I found this recipe on one of the aquaponics forums that I read which can be used to repel/kill those pesky bugs and catepillars on your plants. This doesn’t have to be used for an aquaponics system btw.
Get a couple of hot chilis, seeds and all and add to a blender. Throw in a couple of cloves of garlic, skin and all. Add a little hot water (doesn’t have to be boiling) and blitz until as smooth as possible, then blitz some more. Strain the liquid through muslin cloth, or an old tea-towel into a spray bottle and top up as required with warm water. Some people at this point add literally one or two drops of liquid dishwashing detergent, I do sometimes but mostly I don’t worry about it. Leave to stand for a few hours, overnight is better. You can make up a big batch of the concentrate so you’ve always got some on hand. It keeps in the fridge for a week, sometimes a bit longer.
Spray directly onto both sides of the leaves of plants and any bugs you see. Apply daily.
On the WWW you’ll see similar recipes where they add oil, DO NOT do this as it can make its way into the FT and leave a film on the water and the fish’ gills.