Yet more about canister filters

[Gramazing]

I didn't want to hijack the second thread about flow/media in canister filters.... but someone asked a question that was on my mind and it is related to my intention to buy a canister filter.

I want to get a Rena Xp for my 55 gallon tank. Someone asked what was really the basis for the consensus view on this board that it's best to get a filter that is rated for twice the tank size. I have choice between an Xp2, rated for up to 75 gallons, and an Xp3, rated for up to 175 gallons. There's nothing rated for precisely or even approximately twice my tank. I am concerned that an Xp3 might be too much, by which I mean the outflow might be too strong. Can the flow be adjusted? Or would a 2 be enough for my tank? It's not overly stocked as you can see in my sig. I would want to take down my Whisper filter and save it in case of emergency: i.e. I don't want to run two filters.

[Cliff]

From what I found when looking into canister filters is that the manufactures typically calculate the flow rates with the canister empty. Once you put the media in, and stuff starts growing and collecting in there, the flow is reduced a lot. You have to find the “fine print” that describes the flow rate with the media in the canister.

I friend of mine has a XP3 on a 55 gallon and she likes it.

I don’t know if you can adjust the flow or not on a XP3. I have a fluval 405 on my 55 and you can adjust the flow on that model

[MCHRKiller]

Forget filter ratings, just throw the "up to XXX tank size" on that box out the window it has honestly little to no reference. Instead look at the GPH, even this is a bit far fetched as that is the GPH without media and on a brand new motor without alot of headheight. Take into consideration being loaded with media, and some general wear on the filter expect the GPH to drop up to 40% realistically. So your 350GPH XP3 canister will actually be running at about 210GPH. Its not just canisters that experience this decline...all filters fall into this drastic reduction of performance as what is printed on the box. Canisters need a minimum turnover of the tank of around 4X actual water volume. Of course your tank also doesnt hold the 55G you are promised as that number is based on outside measurements filled to the brim, as well as displacement of water with decor and substrate. Your tank honestly probably holds about 45G of water...so you would need a canister filter with a turnover of atleast 180GPH. So the XP3 is a bit of an overkill...but not so much that it will be an issue. The XP2 having an actual turnover of just around 180GPH is just large enough for your tank, so it would do a fine job of course...but the XP3 would do it even better. Of course you must take into consideration your stocking load, and the individual fish your keeping in general before making your decision.

Just thought I would mention also that HOB filters also should be expected to have the 40% decline, and due to their smaller media volume you should expect to have atleast 6-8X turnover of actual projected water volume using one of them. Of course if you do a combo HOB/Canister then you can split it down the middle on both and be fine.

[Algenco]

I run an XP3 and a hob on a 55

[Gramazing]

I run an XP3 and a hob on a 55

Wow, that's a lot!

[Gramazing]

Thanks for your input MCHRKiller.

Of course the difference in price is not that much between the XP3 and 2, so the precautionary principle should really apply and I should just pony up and get the bigger one. My only real concern therefore is whether it would generate a lot of current in the tank.

[MCHRKiller]

Not at all, it comes with a spray bar so you will get good circulation but not current. I like Algenco used to run an XP3 and a large HOB on a 55G planted without any issues.

[ILuvMyGoldBarb]

I will point you back to that other thread and point out that it is entirely up to you what approach you want to take to filtration. While the XP3 alone, or the XP3 + large HOB is not necessary, it is certainly not wrong either, it is simply one approach to filtering your tank. The XP2 will be a lower flow approach and again, not wrong, simply another approach. It is entirely your choice, neither is wrong and neither is better than the other. The important thing is that you achieve sufficient filtration for your fish.

the GPH without media and on a brand new motor without alot of headheight.

I think you may find that applies to all but the Eheims. I recall reading somewhere that Eheim actually gives your the GPH with the filter loaded with the manufacturer suggested media setup at a standard head height.
Have a look at this test that was run.
http://www.plantedtank.net/forums/eq...rformance.html

While the Eheims did not achieve their advertised flow rates, the flow rate on an empty canister was no higher than one with a full canister of media. Just something to think about.

[lowlight]

I run a Rena Xp3 on my 55 and like it a lot. There are a number of set up options, spray bar or jet. There is an attachment that hooks up to the return tube to control the flow. You can even attach an air line to the attachment if you want more oxygen in the water. Keep in mind that the minimum distance from the top of the motor to the water surface can be no less than 24".

[Gramazing]

I will point you back to that other thread and point out that it is entirely up to you what approach you want to take to filtration. While the XP3 alone, or the XP3 + large HOB is not necessary, it is certainly not wrong either, it is simply one approach to filtering your tank. The XP2 will be a lower flow approach and again, not wrong, simply another approach. It is entirely your choice, neither is wrong and neither is better than the other. The important thing is that you achieve sufficient filtration for your fish.


I think you may find that applies to all but the Eheims. I recall reading somewhere that Eheim actually gives your the GPH with the filter loaded with the manufacturer suggested media setup at a standard head height.
Have a look at this test that was run.
http://www.plantedtank.net/forums/eq...rformance.html

While the Eheims did not achieve their advertised flow rates, the flow rate on an empty canister was no higher than one with a full canister of media. Just something to think about.

That's a very interesting test. As someone said, their pumps must have a high torque in order to be unaffected by the increase in load from adding media. I wonder if Renas behave the same way.