Update 11-02-2016 9:50 PM MST

One thing we have learned through experimentation is that if you pump fish tank water through a water based system, be it DWC or NFT, your plant roots will act as a fish effluent filter with the results you have seen. The water being supplied to these grow troughs must first be filtered, either mechanically or through mineralization (as descrided below), in order to remove the suspended fish effluent.

As we do not believe in removing the solid fish waste from the system (thus throwing away half of your nutrients and most of your minerals, see Aquaponics 101, Part 6: Improving Water Quality), some form of filtering must be done prior to the fish tank water entering the troughs. One way to accomplish this, to a degree, is to first send the water to your deep media beds where much of the effluent will settle out and be mineralized, assuming you have designed them to be large enough to accomplish this. The water coming from from your deep media grow beds can then be routed to your troughs, and if they are lower than the media beds and higher than your sump or fish tank, then no additional pump will be required.

The second way is to use a mineralization tower as described in Aquaponics 101 Part 6 and flow the water from it to your troughs.

The third, most effective and more costly way, is to mechanically filter the suspended fish effluent solids out of the water and then send them to the mineralization tower for processing. This requires a filter capable of removing solids above 20 microns or less, thereby preventing them from entering your clean water path. You then send the clean water from the filter to you grow beds and troughs and return the mineralized water from the tower back to the pump input by way of a tower sump tank for another trip through the filter.

This process not only sends clean water to the troughs but also to the media grow beds allowing for cleaner media and the ability to support more autotrophic bacteria, which will be needed to process the additional ammonia produced by the mineralization process. It also makes the mineralization of the solids very efficient, thereby enhancing the overall system efficiency. It allows for the doubling of the number of plants as compared to a system that removes the solids and discards them.

Oliver