Gallons per hour vs aquarium size

[fishb0ne]

I've always wondered about this but was always affraid to ask
What's the relationship between GPH and tank size?
This question popped in my mind because I've been looking for a small filter for my 5.5g aquarium.
I've been looking at filters that are supposebly designed for aquariums UP TO 3 gallons. However, tech specs say they pump 20gph.
Wouldn't they be plenty adequate for a 5.5g?
Is there a rule for calculating appropriate gph rating?

 

[Fishyfanatic]

For a tank with normal fish (not Bettas or other fish that prefer little water movement) I run a filter with a 10x turnover rate per hour for a hob. For our 29 gal tank I have a filter that runs 300 gph.

 

[Zagz]

It's true that different fish require different filtration. African cichilds for example should have 15-20 times GPH. For most community tanks 10x turnover is usually good.

 

[An t-iasg]

I usually don't go by the suggested tank size in the filter description. I look at the gallons per hour and calculate as Fishyfanatic and Zagz said - 10x per hour for community fish, more turnover for messy fish, and less turnover for fish that prefer less water movement. I have a canister filter that is rated for a 20-40 gallon tank on my 10 gallon tank. I used the gallons per hour rating on this filter, which was 80 GPH, to determine its suitability for my 10 gallon tank. The flow is pretty good in my 10 gallon tank. I have added another small water pump for some additional water movement. I can't imagine this filter in a 20 gallon tank, as the description suggested.

If you are looking for a good filter for a 5.5 gallon tank, I use the Duetto 50 filter in my 5.5 gallon betta tanks.

http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=3632&N=2004+113424

It's suggested for a 10 gallon tank, but it's fine in the 5.5 gallon tanks. It has an adjustable flow control. I have mine set about halfway open. I did also remove the carbon insert and added filter floss, which probably slows the flow a little.

 

[7Enigma]

Just like the inch per gallon "rule" for stocking filter flow amounts are largely variable. More turn over is always better (obviously), as long as you are not stressing the fish by causing them to "tread" water.

I think 10 X turn over is a good general rule of thumb. Tanks with plants, under/overstocked, "dirty" fish, etc. all change the filtration needs.

IMO more important then the amount of turn over is how/where the intake and output is handled. Canister filters will always have the advantage of being able to most efficiently turn over the tank water, while HOB and sponge power filters less so.

If I wasn't injecting CO2 into my tank (and thus trying to minimize surface agitation), I would have a waterfall "slide" where the water coming out of my HOB filter would get carried to the far side of the tank. Then I would be more confident that the water that is being sucked up didn't just get spit out!

So bottom line is that turn over is not the only important factor, IMO as important is where the water came from (and is going).

My 0.02

 

[fishb0ne]

Well, I'd like a versatile filter more than anything.
The Whisper 10i is problematic because
a) it's big
b) no flow control
c) damn tall at over 7 inches, which makes it noisy and fairly hard to use for low-level water situations

Thanks for all the info. Now, does this turn-over "general" rule apply to ponds as well? What concerns me now is that my dad's 6000-gallon pond has a pump which is only rated at around 5k GPH.

An t-iasg, what do you NOT like about your Duetto filter? I might actually get one, at 12 bucks or so on Dr Foster & Smith I don't think I can go wrong. And forgive my ignorance, what exactly is filter floss? I assume it's good for the bacteria colony?

 

[Zagz]

Can't help you with the pond info.

Filter floss is used in place of carbon filters quite often. It polishes the water and removes fine particles. An example can be found here . I prefer to use 100% pure polyester batting for pillows. As long as it isn't hypo-allergenic, it is much much cheaper.

 

[An t-iasg]

There are really no bad points about the Duetto filter. It has a good flow without being too strong for the bettas. If you open the flow control all the way, the flow will still be good for a 5.5 gallon tank if you don't have a betta in there. You can also position the output nozzle. I have mine aimed partially at the back tank wall to lessen the force of the flow a little more, for the betta's sake.

If you do use filter floss, get it really wet first before putting it in the filter. Then submerge the filter in the tank to get it filled up with water before closing it up. It may take 5 or so minutes to start the water flow again after being opened, but you can try to minimize that by getting as much water as possible in the filter chamber before closing it up. You can also wiggle it a bit (while it's attached to the tank wall) to get the air bubbles out. If there is a bad point, it's that it is hard to open/close at first. Maybe I'm a weakling.

Don't get the Duetto Mini for a 5.5 gallon tank. It is rated for a 3 gallon tank, but I saw one and I can't imagine it doing much filtration on anything but a 1 gallon tank.

The filter floss, like Zagz says, polishes the water and removes small floating particles. The bacteria will reside in the sponge inserts so you don't have to worry about changing the floss every week. The small front sponge is primarily for mechanical filtration. The water contacts this sponge on its way into the filter. The main biological filtration sponge is the larger one on the bottom of the filter. I rinse and squeeze the small mechanical filtration sponge weekly. I dip the body of the filter, with the large biological filtration sponge still inside, into the bucket of old removed tank water to rinse it. I don't squeeze it out or handle it too much.

 

[fish 'n' fries]

I have a Supreme brand ovation-210 in my not-quite 5 gallon tank. I love it. It's for either terrariums or tanks so you can put it on its side or upright. It's also smaller than the duetto--which is why I got it instead--(5 1/4" x 1 1/4" x 1 1/2"). I found it at my LFS...didn't see this brand at any of the chains...but don't know if you could get it on the web or not. It's supposed to be 53gph and only requires 6 inches of water. I've had mine since November without difficulties (knock on wood!) The only bad thing is the flow's not adjustable (I have the output pointed directly at my driftwood to keep the bettas from being blown across the tank.)

 

[7Enigma]

And forgive my ignorance, what exactly is filter floss? I assume it's good for the bacteria colony?

If you decide to use this (I highly recommend it) go to an arts and crafts store. In the NE that is a place like Linens N' Things or AC Moore. They have pillow-sized bags of the 100% polyester fiber fill for ~$3. I just rip off a hunk, rinse it quickly in the sink (probably doesn't do anything but just to be safe) and then add it to my HOB filter. Here's a pic of the order I use it in (flow comes from the bottom and goes out the top). The white layer is the filter floss.

HTH

 

[fishb0ne]

Awesome! Thanks guys.
I'm getting the Duetto DJ-50 then

 

[An t-iasg]

You'll be happy with it!