How can I organically get rid of aphids in my aquaponics system?

Question

Hundreds of aphids have decided to take up residency on the various veggies in the aquaponics system I help maintain; gorging insidiously on the plants and multiplying by the dozens. If not stopped soon, I fear it will be too late to turn things around.

My relatively small recirculating system consists of two long/shallow grow basins (containing mostly lettuces, broccoli and parsley at the moment) connected to three barrel-like barramundi tanks housed in an adjacent space; we cycle the water through continually and maintain a constant growing temperature to ensure optimal crop yield. It's not a half-bad set up if I don't say so myself, and annoyingly these pests seem to think so too!

We need them evicted as soon as possible for the greater good of the plants, but doing so is proving a challenge. Any chemical or kitchen remedies for aphids - like the garlic and vinegar solution - were immediately scratched, since anything we spray on or around the plants will get into the water and effectively be sprayed on the fish as well. Hearty as they are, I'm sure barramundi don't particularly enjoy breathing garlic water. Plus, we're an all organic system.

So, any ideas on how to tackle this problem?

Answer 1

Unfortunately the products that can control aphids are either not organic or they are organic, but also toxic to fish (ex. pyrethrins).

It seems like you've got three options:

1. Manual control - you systematically poke through each plant and smash the aphids OR you can use a strong jet of water to dislodge them (at which point they become Barramundi food?). This will take diligence and regular intervention as it is unlikely you will completely eradicate them.

2. Disconnect the terrestrial system from the aquatic system for a period long enough to treat the aphids with pyrethrins and to allow those pyrethrins to degrade. They break down relatively quickly in UV light.

3. Start over - here again you'll want to disconnect the terrestrial component from the aquatic. Then remove all the plants and planting media, sanitize the containers and hardware, then finally install new media and replant.