Together, they generate a fairly strong current in my tank, but for my fish/stocking level, that's a good thing.

I have two fluval 405s running on my 75 gallon goldy tank. My advice, go without the air stone unless your fish indicate they need more oxygen. That said, plants require CO2 (carbon dioxide), and too much surface agitation will result in too much CO2 leaving the water. Surface agitation is required for gas exchange, so if you position your filter return head near the surface, this should agitate the surface enough to facilitate gas exchange (getting more O2 back into the water). faster gill rates, or going to the surface gasping for 'air'. Air stones aren't necessary unless you find your fish 'gasping' for oxygen. The higher the temperature, the less oxygen can be 'held' by the water. The higher the population, the higher the demand for oxygen from your fish. Regarding oxygen levels - your oxygen levels are affected by population and temperature. Amm should always be 0, NitrIte 0, nitrAte 0-10ppm (plants require nitrAtes, so 5-10ppm would be fine)

You will get an idea of whether your filtration is handling the load by monitoring your ammonia, nitrIte and nitrAte levels. In general, the bigger the filter, the bigger the biological filter area, the more b/bacteria can live, the more waste they can handle in a given time. I personally recommend at least 4 times an hour.Ĭonsider that in most rivers, the flow/turnover of the water is probably a lot higher.Īs you add to your population, the bio-load on the tank increases, meaning more waste that needs to be filtered, so by over-run, I am referring to the filter's beneficial bacteria colony size being able to handle the load. I have a 70L tank, with a 440l/h filter ( Eheim 2213 Canister), meaning my water is turned over approx 6 times an hour. Some people will advise a filter capable of turning over the water 3 times and hour, 4, 5 and 6 times an hour. On the filtration side of things, there are varying opinions of what is necessary.

Fluval 403 filter manual