Changing Of Gravel

Watcher74

Watcher74

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Feb 5, 2004
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If you have a tank with a power filter that contains a fairly good sized biological filter in it, and the tank is fully cycled, would completely changing out the gravel cause the tank to recycle?

The biological filter is full of this brownish goo. That's beneficial bacteria isn't it? I can't find it anywhere else in the tank in a visible quantity except the filter.

There is no UGF or RUGF or anything else except a bubble wand under the gravel.
 
The brownish goo is mulm.... you can't see the bacteria.. but the bacteria will live on that mulm. The term "biological filter" applies to the bacterial action of converting Ammonia to Nitrite, Nitrite to Nitrate etc.. it doesn't apply to a device. I assume you mean your powerfilter? Or some form of filter media that your bacteria lives on?

Bacteria will also live in your gravel, however changing out your old substrate for a new one may not cause more then a mini cycle to occur. It "may" not even make a noticable dent in your your water parameters.
 
Right, I know that the term "biological filter" simply referred to wherever your beneficial bacteria resides(such as the gravel in a UGF set up). The power filter just provides a little condo for the guys.

Thanks for the answer. Mulm? Never heard of that before. Time to do a little research.
 
TBH, I'm not sure the gunky stuff is just mulm. It could be many things; after all this is stuff in a filter you know. Mulm is like sperm, eggs, and other (possible) reproductive liquids. I dont think thats the brown slime we have in our filters. Probably just the bacteria colony.
 
Assuming that you aren't overstocked and the fact that you aren't using a UGF, or RFUG there shouldn't be a big problem with changing out your gravel. Without the undergravel filtration, the bacteria in your substrate is greatly limited by the oxygen it can recieve. You will lose a lot of bacteria, but at the same time you will be keeping a lot in your filter media. Nitrifying bacteria grows pretty much anywhere it has a surface t can "hold on to" (for lack of a better term) and it can recieve oxygen and "food" (ammonia, nitrite) so in a non /ugf setup, I would hazard a guess that the biggest part of your bio-filtration occurs in you HOB. Sponges and filter media are great for bacteria colonies. Watch your parramiters for a few days after the change out, Unless you see Ammonia increase you should be fine. and even then you will be way ahead of the game so a few water changes will get you through it.
 
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