AquaClear intake bypass (Adjustable flow)

[Oblio]

So I was looking for the flowrate of my AquaClear 110 and I happened across a bunch of discussions on the Intertubes regarding the adjustable flow rate and the recycling design of the AquaClear HOB filters. One of the claims (and a subject of disagreement between fish-keepers) is that you may get better filtering by reducing the inflow from the tank and increasing the recirculation of water through the media. I was wondering what the experienced folks here thought. I've reduced my filter flow rate down to a minimum so see if there was any qualitative difference, and also to lessen the chance of any fish trauma near the intake until I get a pre-filter. I have noticed that my fish tend to spend more time near the outflow since I turned the flow rate down, it's like their tank size increased by 20%, so that is a plus in itself.

 

[Colin_T]

Six of one, half a dozen of the other. A slower flow rate gives the filter bacteria more time to use the ammonia and nitrite in the water that is in the filter. However, it takes longer to filter the entire tank volume.

A faster flow rate means the filter bacteria have less time to deal with the ammonia and nitrite in the water that is in the filter. But the tank volume gets turned over more frequently.

It doesn't make a lot of difference to the filter bacteria. However, if you have fish that come from still or slow moving water, then a slower filter flow is better for them.

 

[Oblio]

ix of one, half a dozen of the other. A slower flow rate gives the filter bacteria more time to use the ammonia and nitrite in the water that is in the filter. However, it takes longer to filter the entire tank volume.

Thanks @Colin_T , kinda my thoughts too. The other thing that I considered was that once the contaminants are in the filter housing, re-filtering (via the bypass) is more likely to trap them vs dumping them back into the tank. If they are dumped back in the tank, a portion of those may not make it back for another go through the filter. This is more relevant for heavier particles that might settle out onto the substrate, fine particulates that stay suspended would eventually get re-filtered.