Rocket Season, bioballs aren't necissarily a hotbed for nitrates. In this example in a no light, low oxygen environment they can actually have a de-ditrifying effect. However there are several things to consider. The flow would have to be very very slow in order to accomplish the low oxygen environment. This is usually accomplished with a long (MEANING LONG) coiled narrow tubing na
dslower flow. The 12" diameter pipe I am affraid would simply mimic a standing sump. So yes increasing your water volume is good, but not for detrification. I like the idea though. Depending on your media, canister filters may contribute to nitrates as well.
itsfishy, if fed via a pump from the tank through a sealed tube with the same pressure returning it will basically be a canister/fluidized filter bed. If able I do still recommend a sump system. You tank is probably a little young for your choice of livestock but dilligence may reward you. So, for just water volume it's a unique idea but for detritrifying propably not.
Still to date the best methd found is a lot of LR
, water movement, water changes, and effective skimming.