"Sharp Tooth" wrote in message
...
On Wed, 17 Nov 2004 20:53:36 -0500, "Nicholas Wise"
wrote:


"Sharp Tooth" wrote in message
.. .

Thanks Nicholas,

I guess since I haven't been vacuuming the gravel, my three tanks
which have been set up for two years have essentially had no
filtration during that time.

It's not that they've had no filtration. The bacteria still colonize the
top of the gravel and any other exposed surface, it's just that the
undergravel filters will not work properly w/o a clean substrate. The whole
concept behind them is that the water is pulled through the gravel,
providing mechanical filtration of a sort and it is then passed through the
undergravel plate where large colonies of bacteria then do the bio
filtration for you. You can see where this breaks down if water flow
through the gravel is limited.

Would it be okay to mix the fluorite with regular gravel to save a
little on the cost?

Sure it would be. Obviously it is not as good as pure flourite, but is
still better than none. I would recommend at least a 50/50 mix. Another
way you could save on cost is with a layer of material under the flourite
like a peat moss/cat liter mix. I've done this with great results. Good
luck!