Tropical Fish Keeping - Aquarium fish care and resources

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Mattfish 01-08-2012 10:30 AM

New to aquariums! Can you over filter your tank?
Hello everyone,
First of want to say hello to everyone in this forum looks like a nice friendly place to be :)
I currently have a 24 litre tank and a 500L/H hang on filter for it (cycling as we speak) and my question is,

Can the tank be overfiltered and if so why is this a bad thing?

I had an internal filter which came with the tank but it was a rubbish thing which i think didn't filter properly as my fish died quite quickly (I had cycled for 9 days before hand before anyone asks) i now don't use it and use my new filter now.

Hope you are having a wonderful day and a response to this would be most appreciated as I really think i can get into this more so and don't want to waste money buy doing something differently so i don't kill the fish :P

Nubster 01-08-2012 10:39 AM

Not sure that a tank can be over filtered per say but there can be too much flow which is what will likely happen with too large or too many filters on a tank. Depending on how many fish, plants, how messy the fish are, how much you feed, ect., you generally want a filter that can turn over the water around 6-8 times per hour. That's just a guideline. You may get away with less, you may need more.

On another note, 9 days does not make for a cycled tank. It usually takes 4-6 WEEKS to completely cycle a tank unless you are using some sort of seed material, and I'm not talking about the rubbish in a bottle. Putting fish in an uncycled tank then not properly caring for them is what kills them, not a bad filter.

Mattfish 01-08-2012 10:55 AM

Thank you for that ill keep cycling then, the tank would be easily filtered like nine times at least an hour :)

AbbeysDad 01-08-2012 12:43 PM

Welcome Matt!

Ah...filtration, one of my favorite subjects. There is a current myth that filter water flow must be 4-10 times the size of the tank in GPH. Good filtration is not about how fast or how much water is pushed through a filter, but rather how well we filter the water. In fact, water flowing more slowly through very fine media filters the water better than blasting through coarser media. Running all of the tank water through a good filter 2-4 times per hour should be more than enough if we're doing it right. As a matter of fact, some folks with heavily planted tanks use simple bubble up sponge filters that process very low GPH since plants help filter the water. Detritus can be allowed to decay in the upper layers of the substrate to help feed the plants or can be removed with a gravel siphon hover above the substrate surface.

Some folks seem to thing they have to have all kinds of water flow to move detritus into the filter inlet. (I hear all the time about folks adding power heads in addition to their filters).
It's almost impossible to do this and many of our fish don't appreciate these high flow rates in the tank. It's far better to let mulm collect naturally on top of the substrate and remove weekly with the water change - or better still, if it's a planted tank, just let it decay and help feed the plants.

It takes 4-8 weeks to cycle a tank unless significant biology is bio-seeded into the tank (and about 6 months before the tank is considered 'established').
For instance, if we took a filter or filter media and some substrate from an established tank to start a new tank, we could add some stock right away as there would be enough biology to handle the bio-load.
Also, if the tank is medium-heavily planted, cycling is not required as the plants will process the ammonia directly.


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