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Re: lower light

> Tom -
> In the low light tank you are experimenting with, what is the fish load ?
> How much fishfood is going in? My assumption about the need for high light,
> is that the fish load contributes a lot of phosphate which needs to be
> compensated for by a correspondingly high input of all other parameters. If
> that low light tank doesn't have many fish, what might happen if it is
> populated?
> Tom Wood

I recently did some heavy fish loading of a pair of tanks to see about this
notion. I'll talk about that later.

The tank in question is not heavy, quite the opposite, few fish. I have to
add KNO3, KH2PO4, TMG etc every 3-4 days. But adding fish would mean less
KNO3 only. PO4 does not cause problems unless you have poor CO2. So it's
contribution tends not to be of much consequence. N species are the big

 Fish loads add NH4 and NO3. NO3 by itself doesn't cause a great deal of
algae but a small amount of NH4 certainly does. Try it sometime to see if
you wish but have some caution since things like ammonium sulfate and high
loads will cause nasty algae outbreaks kill fish if overdosed etc.

 High plant/low fish ratios can handle this small amount of NH4 coming in to
the system. Low plant/high fish ratios have trouble and get algae. This is
the reasoning behind the fish load recommendations. When talking about N
there are a few different species of N. This does make a difference as to
which type.  

As far as PO4 from fish foods feedings, I really doubt one could build up
anywhere near enough PO4 before their next water change to cause any problem
provided they have CO2 even in a low light tank. It's the NH4 waste that's
causing the problems. A bigger filter/more plants/less fish/more water
changes/bigger tank etc would compensate for this. Anything to convert the
NH4 fast before the algae sense it's there in the water. Not enough plants
to uptake the NH4 fast enough.

Adding high light will use things up faster but will also activate the algae
when the NH4 is there and allow them to grow faster so your damned either
way it seems to me. At lower light you can react faster and take the needed
steps to cure things. Deficiencies, algae etc all become easier to deal
with. But the plants grow slower, not as bushy etc. Just keep the fish loads
moderate is the best. Absent, too many etc is no good. Some slight low
levels of NH4 is good for a tank.
Tom Barr