Filters - Is there anything wrong with two or a larger size?

thebrok2

Registered Member
Jun 7, 2009
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I have a couple quick questions. I am trying to understand the bacteria that is held in a filter. When I change a filter cartridge will I loose my bacteria that happens when the tank cycled?

Is there any harm done by running two filters to help maintain the natural bacteria while one filter is changed?

Is there any reason to not get a larger size filter? For example if I have a 20 gallon take could I get a filter for a 30 gallon tank?
 
It's good to overfilter in most cases. Two filters is a good idea. Most filters have bio pads in them that never get changed so most of the bacteria would be in there anyhow.

Welcome to AC!
 
if the tank is cycled no worry of needing 2 filters, the rocks have the bacteria in them and you wont go through a cycle again.
its always best to over filtrate. the box may say 20-40g but its usually not enough flow for a 20 or 40.
if you have a 20g i would get a filter for 30-50g
i use the aqua clear filters and always buy a size up or 2 sizes up.

if your tank has some plants in it i wouldnt use the carbon filters either there a waste of good money, i havent used carbon for 4 years in all of my tanks plants or not with no problems. i use and alot of others use 100% polyfill. they sell it at walmart and its cheap 3.50 for a pillow size bag, just rip some off and put it where the filter sleeve usually goes. replace every 2 weeks or whenever it gets dirty.
its cheap and works great, you will save alot of money not buying those blue or white filter inserts ever again.
 
Many people (me included) run more than one filter on certain tanks for many reasons. There is no single reason stating you must or can't do it.

As far as your bacteria goes, yes you lose what is on the pad, however that is not of a majority quantity to cause your tank to recycle. The majority of beneficial bacteria resides on all hard surfaces, i.e. the substrate, the glass, the walls of the filter, etc.

"Filter sizes, should you go larger?" Only you can answer that question. Depending on what you stock and how much, is your deciding factor. If you stock "messy" or "dirty" fish such as Oscars, plecos or goldfish, not only larger but also redundancy is preferred. I look for a flow rate equal to 6 to 10 times an hour turnover of water. For things that have a low bio-demand on the tank system, I will go with a lower rating.

As an example, if I want to filter a 20 gallon tank I may use a filter that has 160gph advertised rating, or I may use one that has a 200gph rating depending on the stock. In the case of my Oscars and plecos (messy fish) I use 2 Marineland Emperor 400's on each end of the 90 gallon tank to help eliminate dead spots ad to suck up as much waste as possible. Doing so gives a combined filtration of approximately 800gph equaling an 8 times an hour turn-over rate. When using the advertised flow rate that gives me a theoretical 7.5 gallons of water each minute filtered.

Do what is right for you and your fish. Keep in mind when a manufacturer states it is good for 30 gallons, it may mean filtering 30 gallons at 4 times an hour or it could be 6-8 times an hour. There is no industry standard for what is an acceptable flow rate.
 
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