I figured this may be good discussion fodder...

Fishypaw wrote:

the inch of fish per gallon is a decent rule of thumb guide for stocking i find. in general a tank is not 'mature' till about 6 months, at this point u can then consider stocking to a 2 inch per gallon level. take into acount your filtration also. if your filter is turning over 2 times the tanks volume an hr it is ok, but to be good i'd be looking for 4 - 10 times per hour, especialy if u have a lot of plants and more delicate fish like cichlids.

I'd read that 4 times an hour is optimal. When I bought my Eheim 2217, @1200 l/hr for my 250 litre tank, I had that in mind.

My 33 litre tank, had a Fluval 2 running at 360 l/hr, so that's turning over at about 11/hr. I recently added the Eheim2213 to that tank @440 l/hr, that's a turn-over of say 13/hr.

Close on the same throughput on this second tank, but whereas the filter volume of the Fluval was about 400ml, the Eheim has a lovely 3 litre volume. Lot's more bacteria !!

I have an emperor 400 and magnum 350 on my 50 gallon along with an UGF. The tank gets filtered 15 times an hour, not including the UGF.
The 140 gallon will have 2 emperor 400's, 2 magnum 350's, 2 802 powerheads and 1 501 powerhead with quick filters. This tank will be filtered almost 11 times an hour excluding the powerheads.

Nice topic for discussion and one I've been doing some reading on while planning the tank rack (still wanting to centralise it at some point).

I was going to write a nice long post but

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explains a lot of it better than I could. Using the formula on there though you probably want to aim for about 6x per hour turnover to achieve a good (99.9% effiency per hour) level of filtration.

What are the specs of these devices Funky? Do the '400' and '350' relate to a throughput gal/hr? What are your Filter sizes (Volume/Capacity)? Which ones filter, and which just pump?

I'd like to read your version too, Monkeh. I'm printing this one to return with. Although I did note one early paragraph, re the mixing of filtered with unfiltered, before going through the filter again.

Hence filter/pump capacity (L/hr or Gal/hr) never truely relates to 'tank cycled' capacity (Vol/hr).

I have a corner right below my spray bar, and off to the side of the pump inlet, you can see the crap in suspension, just going 'round and 'round. It's a good siphon spot, that.

Is this reading to do with your "Sump", that I asked you about many moons ago?