Turnover in the tank is a good thing. How is your skimmer being fed? Most use a pump (mine uses a Mag 9.5) therefore the return pump has no bearing. As for the De*Nitrate:
Fromthe SeaChem site:
Live” rocks or reef rocks remove nitrate by anaerobic denitrification. de nitrate™ removes nitrate by the same process. Efficiency is magnified several folds by forcing the water to filter through the porous de nitrate™. As with reef rock, anaerobic conditions are achieved by the porosity and the depletion of oxygen by the aerobic process at the surface. Excessive flow rates should, therefore, be avoided, as they may impede development of an adequate anaerobic environment to support denitrifying bacteria.
de nitrate™ is also an excellent media for aerobic nitrification and it makes an ideal biological filter in drip trays, canister filters, sumps, or even box filters. At high flow rates (greater than 100 US gallons per hour), it will function solely as an aerobic filter
. At slow flow rates (less than 50 US gallons per hour), it will function as both an aerobic filter and an anaerobic denitrifying filter.
For best results, de*nitrate™ should be placed to assure the flow of water through it, such as in a canister filter, chemical filtration module, or box filter. Flow rate should not exceed 200 L (50 gallons*) per hour.
If higher flow rates are unavoidable, use Matrix™ or Pond Matrix™. It is best to rinse off dust before use. Once de*nitrate™ has been in use for several days, nitrate concentrations should start to fall and level off gradually at a concentration of about 4–5 mg
/L as nitrate. As long as nitrate concentrations remain under control, the product is not exhausted. Each 500 mL of de*nitrate™ treats about 100–200 L (25–50 gallons*), depending on initial nitrate concentration and the current biological load. Enough should be used to remove nitrate at a rate at least as fast as the rate of formation. If very high nitrates are initially present, they should be brought down to less than 20 mg
/L with water changes.
So you may want to put it in canister and feed it via a seperate pump. I have some in my sump. It's just in a bag in between the baffles sitting on top of a poly filter. Guess I have too much flow for it be effective too <g>
Please keep us posted on your progress.