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Re: Optimum current in planted tank

From: "Frank I. Reiter" <FIR at istar_ca>:
>Recently, I setup a pair of 120 gallon heavily planted tanks with a Fluval
>403 filter on each one.  Continuing with the original plan, today I also
>added a Seastorm 240 fluidized bed filter to the output of the Fluvals.
> ... more related stuff about the current flow...

Frank, you might want to reconsider having extra biological filtering at all.
If you have a heavily planted tank, the plants themselves are the best 
biological filters for your tank.  They'll consume the fish's ammonium waste
directly instead of converting it to nitrates.  

I just have a Hagen 402 powerhead without any filter material in the "quick
filter" cartridge that I got with it.  The cage keeps snails and small fish
out of the filter, and the circulation is unimpeded by a filter.  I had some
Kribs spawn a couple of months ago and for some time I had more "fish inches"
than was recommended for my 45 gal breeder tank, but since I had enough 
circulation to keep the surface moving (not *turbulent*, just moving), I had
enough oxygen (thanks also, I bet, to the plants) to keep them all healthy,
happy and growing fast.  If the plants didn't consume all the ammonium, enough
bacteria grew on the plants and substrate to take care of the rest.  I had NO
ammonia problems.  I *did* have a nitrate problem, but I think that was because
I had so many fish to feed.  

Extra biological filtering is a brute-force way of keeping ammonia in check. 
You don't have to resort to it if you have a large enough plants-to-fish ratio.
It *is* nice to have something filtering out large particles like floating 
waste and leftover food, but it doesn't have to be used continuously.

I don't have a quantitative answer to how much current you need.  You need 
enough to circulate nutrients to and from the leaves of your plants, but some
plants like higher current than others.  Some plants like to grow in corners
where mulm collects at their base (some Cryptocorynes, beckettii comes to 
mind), others like more constant flow of nutrients and/or use the current to 
clean the leaves and keep the plant stem horizontal where it can get the most 
light to its leaves (Limnophila, Cabomba in my experience).  

Ask around about your particular plants and see what kind of suggestions you
get.  Look at the Tropica site (http://www.tropica.dk), they are a good place
to start.  Play a little with it and watch your plants like a hawk. You might 
be surprised how little current you really need.  I'd definitely leave out
the fluidized bed filter anyways, unless you plan on having more fish than
you're comfortable allowing the plants to handle.  Keep in mind that the bio-
logical filter is COMPETING for nutrients with the plants, so don't over-do it.