advice on fluval filter size

[pberm1962]

ive had a 26 gallon bowfront tank set up for about 6 months. im using the fluval 207 canister filter . its running great and ive had no casualties.i have healthy,active danios and mollies.i have 11 fish currently.. i am going to a 36 gallon tank and am wondering if i need to step up to the fluvall 307. the specs on the 207 claim it can filter up to a 45 gallon tank so i will use that unless i hear a contrary opinion from you folks. hopefully you can give me your tank size and which fluvall you are using . im currently using a spray bar off the fluvall which i have raised off the surface hopefully creating surface agitation.

[Aiken Drum]

There are a few metrics for determining filter size.

You want a filter turning over the capacity of the tank 3 or 4 times per hour. A 207 is rated for about 200 gallons per hours. In practice when set up you will get 100 to 150 gallons per hour. So based on that your 207 will turn over enough water in your larger tank.

You also want it to hold enough filter media. I personally like 1kg of filter media per 100 litres of water. So a 36g tank is about 140 litres of water, so you want say 1.4kg of filter media. 1 litre of media is about 1kg and the 207 has 1.8 litres of basket space in it, Take out say 1/3 the capacity for sponges, and your filter will hold about 1.2kg of filter media. So a little short there, but not way out.

What it all boils down to is a filter is usually good for half its rated capacity. So a 207 is good for about 20 to 25 gallons. However ive never heard of anyone having filtration issues unless they are way out, especially with canisters. If you want belt braces then upgrade, but unless you are very overstocked or keeping very messy fish (goldfish) you wont have a problem with the 207.

TLDR. If I was buying a new filter i would get the 307. If i had a 207 lying round i would be happy to use that if not overstocked.

[pberm1962]

great advice! as i was getting toward the end of your advice i began thinking that i will go with a new 307 as i will be adding more fish and would rather go a little larger

[Aiken Drum]

Just remember to either run both filters alongside each other for a month or so, or take all the cycled media from the 207 and put it in the 307. This will help cycle your new filtration much easier.

[pberm1962]

ok ty,. again, great advice love these forums and i will try to send pics