Have 70 gallon planted fresh tank with 8 tetras. Filter is a wet-dry under neath. (In a previous life the tank was a marine tank.) All has gone fairly well, especially considering we have some remnants of the marine days... We have an automatic feeder that adds a little acid to the sump 3 times a day. Feeding is also on an automatic feeder, keeping the quantity fairly regular.

In the last week we started developing a lot of froth or foam in the wet-dry. I'm sure its time for a water change, but all previous testing in months past showed 0 for all tested items (including nitrates).

What causes the froth in the wet-dry filter? Another week or so and the bio-balls will be covered!