Originally Posted by BillD
Your nitrates are what they are because the filter is working. Adding another filter will not change that. filters are nitrate factories. For lower nitrates more frequent filter cleanings and/or more frequent or larger water changes. Adding another cannister to hide/store debris in will not help/change your situation, in terms of nitrate levels.
Yea, what he said. Nitrates are just the end product of the fish food. The fish convert the food to ammonia (uneaten food decomposed into ammonia), the filter converts the ammonia to nitrate (two step process... becomes nitrite first).
So more filters in the same tank just means the speed at which ammonia becomes nitrate is increased. So as long as your existing filter can convert a days production of ammonia to nitrate within 24 hours, there is no need for a second filter.