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post #1 of 4 Old 05-04-2007, 09:25 AM Thread Starter
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Undergravel filter

In an undergravel filter, all the beneficial bacteria has to be in the gravel, yes?

I am turning my small tank into a fry tank, and so don't want any gravel in it. Therefore I have to take out the undergravel filter and put in a normal sponge filter. I have the new filter for it currently running in another tank alongside the original one for that tank so it won't be "new" so to soeak when I put it in. What I am wondering though is will the tank still have to cycle, or will it just be a wee mini-cycle?

All gravel and the undergravel filter are coming out. The water will have to be changed to make it easier for me to gtet all the gravel out, then the used filter will be going in. The heater and an ornament will remain there.

I'm a bit confused as to what will happen here?

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post #2 of 4 Old 05-04-2007, 02:46 PM
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you will be having to cycle again but you are going to speed it up a little but not alot since u have the new filter in a established tank if u can get your hands on bio spira. and since all the water and gravel is coming out there wont be any bacteria accept for the filter and if u put some decortations in from the other tank. but no mini cycle it will be a full cycle just sped up
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post #3 of 4 Old 05-04-2007, 03:20 PM
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Even with an undergravel filter you have bateria everywhere. On the sides of the tank, the ornaments, even on the filter. If the filter is seeded really well in an established tank you shold only see a really minor mini cycle at the worst. I took out my undergravel filters after I ran my new AC HOB filters in the tank for 3 weeks and never saw a cycle at all.

They are really messy though so I would suggest having enough water to possible do 2 water changes. There can be ahuge amount of junk under the filter and it can really make the tank look nasty. It took me 4 water changes and lots of sponge cleainings to get all the gunk out of the tank, about 10 days in total.

If you can, get a hose under the undergravel plate and syphon the junk out first as best you can to save some work later.
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post #4 of 4 Old 05-04-2007, 05:00 PM Thread Starter
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Thanks for the advice F4A and xxthrwitdwnxx.

I'm definitely not going to use BioSpira though. It's not available in this country for a start and I don't know, maybe I'm old fashioned but I prefer not to add anything to my tank to cycle it. No surer way of cycling than just doing it yourseolf. BioSpira may work for some and it seems to have worked for you but it's not a guarantee.

I'll siphon up all the junk like you suggested and I'll monitor for a week or 2 (or however long it takes) before I add the fry, but I just wnated to know what to expect before I do it.

Thanks again.
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