About two weeks ago, we removed the fish from one of the four tanks that comprise our new Aquaponics set up.  I shut off the air to the tank but left the pump running so the grow beds continued to flood and drain.

While the tank is still being aerated by the water cascading back into the fish tank from the grow beds, I've been interested to note the amount of solid waste that has settled out.  I've syphoned it off on three occasions but it continues to build up.

I advocate the removal of solids from aquaponics systems (including those with media-based grow beds) on the grounds that solids impair nitrification which has a negative impact on water quality.  The presence of solids also encourages denitrification which drives the pH up. 

What I didn't realise (before transferring the fish from the tank) is exactly how much solid waste is in suspension.

Advocates of media-based grow beds claim that worms will mineralise the fish solids and release the nutrients that are bound up in them.  While this may be true (and I agree that the nutrients should be put back into the system), I'm of the view that mineralising them in the grow beds is probably not the best way to do it.

As things currently stand, I'm limited in the amount of food that I can give to my fish which impacts their growth rate.....so I've resolved to increase the aeration to the tanks and to experiment with various solids removal devices.