Filtration

[matildanz]

I know there are about 4 billion articles on this subject regarding makes and models, flow rates, media etc etc but I'm wondering (well actually my dear 'need to know' husband is) why you can't use multiple smaller filters in a large tank if the combined lph (?) is sufficient. This has come about because I've got a tank sitting in the garage that I need to organise filtration for and we've been looking at external canister filters.

I must stress that he's not a cheapskate (he is infact the biggest gadget freak I know!) but he's one of 'those' people that come up with the strangest questions that I'm in no position to answer!! :lol:

[Ira]

why you can't use multiple smaller filters in a large tank if the combined lph (?) is sufficient.

Who said you can't?

Most people with medium to large tanks do use multiple filters. A lot of the biggest cannisters still aren't enough to filter anything over 400l on their own.

Of course, more than 2-3 starts to get a bit ridiculous.

[spoon]

there is the redundancy factor as well say you have two canister filters and one craps out you still have one good one another feature of this is that you can clean one out at a time a few months apart so you dont lose most of your good bacteria

[suphew]

There are a number of factors that come into play. But firstly don't get too caught up in LPH ratings, it is a useful general guide to the size of a filter but is really pretty meaningless when it comes to a filter's capacity. What we really should care about is the media volume and type of media in the filter, it's the bacteria that is doing the job and this is where it lives, the flow of water to the bacteria is secondary to this.

Small internal filters tend to have just sponges or in some of the top end ones like the fluval U series just a few noodles 1/2 a handful at most. This is a pretty poor surface area for the bacteria compared to a canister full of noodles.

If you added up the power usage of individual internal filters to get the same media volume as even a low end external, you will find you use many times more power.

The intakes on small internals are usually small and will block up pretty quickly compared to an external. Meaning a lot more filter cleaning.

Fish tanks are for looking at fish, not for looking a filters.

Depending on where you live heat might be factor, internals will heat up the water cause they are sitting in it.

Internals are sometimes quieter cause the water bocks the noise, but an external can be shut away in a cupboard so you have more control over the noise. If an internal is noisy even in the tank there is nothing much you can do about it.

One power cord verse many.

There is not really any cost saving, 2-3 internal's will cost as much as the same quality external to buy.

No filtration system is perfect there some advantages to internals over extranals but I hope this helps answer your husbands question

[matildanz]

Thanks guys, I now have one happier husband!!

The 2 canister system makes lots of sense as spoon points out so I think I'll be using up all my birthday and chrissy present credits on filtration!!

Suphew - Thanks for your reply, not only is the other half happy, but I actually understood!! :lol: Yes I have a Fluval U3 and the noodles are pretty pitiful.