Fish In Fish In Cycle

[OldMan47]

I am going to disagree with WD here, a rare occasion indeed. Filter flow happens to be one of my pet peeves. A filter's flow must be high enough that all water in a tank is exposed to the filter several times a day, not per hour. On the other hand, the volume in a filter that is occupied by biological filtration needs to be large enough to accommodate the biological load of your tank. I have old fashioned box filters that probably only move about 1/4 x per hour but do a great job on my tanks as biological filters. Those filters do a great job of maintaining the fish in their tanks. I also have canister filters that provide as much as 7x flows. The only difference that I see between the two setups is that the 7x filters do a bit better job of keeping my substrate looking clean. Both tanks have zero ammonia and zero nitrite readings in them but I must use my gravel vac a bit more carefully on the tank with very low flows. Please examine the biological filter media volume rather than the flow rate when evaluating a filter as being suitable for a particular tank. It will serve you much better to do so.

 

[waterdrop]

Well I've just now made it around to seeing this again and really OM and I don't have any disagreement on this I don't think. We've both examined the full range of filter capacities in the past, from the low end where little old-fashioned box filters are involved to the high end where high-flow cannisters are churning the water and I always felt in agreement. The only thing that happened here was me taking a shortcut and just saying 5x to make a quick statement rather than examining the issue in more detail. I believe OM and I have been in agreement in the past that there's plenty of evidence that significantly smaller flows can do ok and even that media volume can get by in smaller amounts more than most hobbyists like to currently talk about. That said however, I'm sure both of us would agree, as OM has already said, that its highly desirable to have higher media volume if at all possible. For me there's been no comparison between the old small volume box filters and the huge volume of a good external cannister that goes above minimal sizing for the tank. Its like night and day and I really like having the larger volume.

Part of the reason I sometimes shortcut on this topic is that flow rate and media volume typically move upward in lock step, so when you buy a higher flow rate, it usually goes without saying that the filter design will include a higher media volume. But I certainly admit to being somewhat "wowed" by the arguments of the high tech planted folks (sometimes to things like 10x to keep the substrate cleaner and help move traces of ammonia out of spots where algae might be triggered) and allowing that to creep in to my general beginner advice when in fact that's not necessarily the ideal advice for all comers. In many cases the extra needs of a planted tank will not be there and many beginners my benefit from the economic standpoint by not overdoing the filtration.

~~waterdrop~~