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Looking for a more detailed explanation of the flow rate reqs for reticulated hillstream loach

Posted: Thu Feb 27, 2020 10:04 am
by el_miguel_
I have question regarding the filtration capacity required for a reticulated hillstream loach (i.e., at least 10x).

How was this number determined? Are there studies? Is it based on mapping the average flow rate of their original habitats? Is it based on a more nuanced picture of their water preferences (c.f., what we know about trout)?

More importantly, handwaving at how we know, why is it necessary? Is it for wellbeing purposes (i.e., they just really like that level of flow)?

The reasons I ask is I am also an avid flyfhisherman and know that while one might assume that trout prefer fast flowing water (because that is where they are often seen and caught) that they actually only prefer (based on scientific studies) water that moves one foot per second which is considerably slower than the average flow for the rivers they reside in. The reason trout hang out in fast flowing rapids is because its the best way for them to get rapid food delivery but if they arent feeding they arent hanging out in that type of water. So do we know that loaches like it all the time. I also ask because if it is a wellbeing thing then the function underlying the 10x gph rule can be accomplished with a separate powerhead placed in the tank that doesn’t really do any filtering.

Or does the 10x gph rule serve a different function? Does it ensure adequate water quality? Which would mean that if I have a filter that reaches only 8 or 9x gph then I could make up for it with more water changes and that a powerhead wouldn’t solve the problem.

Does it serve to increase oxygenation? If so, this can be accomplished by including an airstone for increased surface agitation, also this means that one could actually still have a wildly inadequate tank even if they have a large enough filter, having been mislead by the lack of clarity over the true purpose of the 10x gph rule. For example, with a bigger filter you can fit slightly more fish but fish take up oxygen and that would mean you just "ate up" the benefits of the added flow (but if its about flow rate for wellbeing, adding more fish wont make a difference, in this respect, because fish cant "use up" flow rate).

In sum, my question boils down to: What function does 10x gph actually serve and also, do we know scientifically, that loaches actually like being in this fast of water ALL of the time or are we just guessing based on their habitat without considering nuance?

I am interested in any and all perspectives!


p.s., the examples/scenarios I give are to illustrate why I am curious about them so please dont perseverate on the minutiae of them, its more about the broad idea of understanding the reason behind the rule because it has different implications.