To floss or not to floss...

[Totenkampf]

That's a good topic for a long discussion.

I think, high flow or low flow, what matters is the amount of active bacteria present on the bio media. I also think that for a bigger tank having a higher flow through rate in the filters and good flow inside the tank is important so that any ammonia/nitrite spikes are dissipated quickly.

That's why I wanted a 8x - 10x tank volume flow through my canisters and 4x - 5x flow through my sumps in all my tanks. So far this rule of thumb has served me well and I'm not speaking for others. When you get to 200+ gallon tanks, this gets harder to do because there aren't any canisters that can offer that kind of flow. At that level, 2x 2262 or 2x FX5 are the best options.

With municipal waste water treatment plants, the requirements are different since there's no way to retrieve water when it leaves the plant after treatment. So it's important to have as much reaction time as possible to get as much junk out as possible.

Since we recirculate water in our tanks between water changes, we can fudge with flow rates a little bit more since the water is constantly being treated as it's being loaded with ammonia.

There's a certain point where flow through the filters has to be enough to handle the bioload being created in the tank. Below that level, the filters can't keep up.

yes, a treatment plant is a linear process and we are recirculating the water to be treated. while chemical interaction time with a recirculating media is probably not so critical because it can do so on a continuous basis, the bacteria must have to have time to convert (eat) the substances that are flowing by it and that is a cyclic conversion. Olaf also describes that bacteria are unable to affix themselves to media where the velocity is greater than 30 cm/minute. i just gave up trying to convert that velocity to a flow rate going throu a 1" ID pipe but let us just understand that too much flow = the bacteria will release and go find a new home. i hypothesize that, in the case if biological conversion, greater flow rate can mean LESS reaction time. if you were standing in a tornado and cheeseburgers kept flying past would they get smaller just because you were there? could you take bites out of them no matter the wind velocity of the tornado? the fact that you DO size your sump flows at a lower rate than your mechanical filtration would speak that you do agree with this at some level?

if you really wanted to increase the biological filtering capacity of a system then you would not increase the flow of the water going through it IME, you would increase the surface contact area of the biological media so that more bacteria could colonize and thus provide better conversion capacity at the same flow rate. in SW, you add more live rock/sand...in FW you basically do the same. read this article on the poret filter and see if it makes sense to you or if not maybe you coudl explain it to me because then i am not getting it like i think that i may be:

http://www.janrigter.nl/mattenfilter/

[SunnyHouTX]

Did some number crunching... I estimate the inside diameter of a 2260/62 canister is about 11". So cross section is about 0.66 sqft. And I'm gonna assume that flow through my 2262/1264 is about 900 GPH, about 120 cubic feet per hour. So flow rate in the canister is (120 CFH)/(0.66 sqft) ~ 182 ft/hr ~ 92 cm/min. So the max flow through that works within Olaf's guidelines comes out to a third of that, about 300 GPH.... I did a back calculation using the numbers from your link and that comes to about 296 GPH for a 2260/2262 size canister set up purely for bio filtration.

Wow...

[eklikewhoa]

IMO, high flow rate is crucial when using as a primary mechanical filter.

[Totenkampf]

Right ek, that's what's rolling around in my head. I'm just thinking that for large tanks especially, a high flow canister set up for mech filtration and a lower flow wet dry with tons of surface area may be the most efficient. Olafs paper suggests that the euros understand that bio and mech filtration in the same system are counterproductive. Well euros other than that eheim guy.

Good Maths sunny, I was done braining yesterday and wasn't converting my units right.

[SunnyHouTX]

I just closed the ball valves on my canisters just before going into the tank by 45°.

[swk]

I run floss on my 2262 in my petro tank. I added it for more mech in the first place, so that's its primary purpose. The sump with 10 gal of bioballs plus japanese pond mats handle the bio just fine I think. I clean mine out every 3 months or so

[eklikewhoa]

Eheims are so much more versatile than it's Fluval counterpart.