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Re: [AGA-Member] Low-light tanks & CO2

It sounds like your nitrates are high but don't error on
the other side of caution and get them too low.

I would try to keep the nitrates around about 10 ppm and
the phosphate around 1 -2 ppm. For potassium, I'd aim for
about 10 but if the potassium is high, it doesn't seem to
present problems. If you dose with potassium phosphate and
potatssium nitrate, you probably have enough potassium.

You can add plants (see previous note on floating water
sprite) to help suck up excess nutrients. Or do more or
larger water changes to hold down the nitrate levels.

In trying to push down your nitrates, you might depress
your phosphates also, so keep an eye on the phosphate
levels and dose if you need.

As for light and depth. there are only two ways to easily
get more light to the bottom, add more lights or narrow the
angle of the reflectors. The latter has only limited
utility because, you can only go so far and fluorescents
tend to scatter light a lot anyway.

Don't worry about whether you are figuring 2 wpg based on
nominal or actual water volume. 2wpg for a medium level of
light is just a rule of thumb not a precise recipe. There
is no precise recipe since each tank can be set up and
behave a bit diff than another -- what plants you have,
which might be shading which, nutrient levels, CO2 etc. can
all impact the overall activity of your plants. Wpg rules
are just a guide but now that you have your tank set up you
can watch how the plants that you grow in that tank behave
and adjust accordingly, either with more lights or
adjusting the lighting period for some or all of the

--- Heather J Gladney <hgladney@comcast.net> wrote:

> At the risk of hijacking the thread here--file it in a
> new category?
> I've been meaning to ask about this for awhile
> anyway...with your 
> indulgence, please...
> I think this one's called, "not enough water changes", in
> spite of the 
> fact there's folks out there who insist you don't have
> to.
> Last testing batch I did:
>  pH 6.7 (down from 7.0 over a month, using solenoid on
> pressurized CO2 
> system.)
> KH 5 (up from 3 over the month)
> GH 13- 16 (down from 15-18--I think this was Mg, it shot
> way up when I 
> added Epsom + Seachem Equilibrium.)
> nitrate about .3 mg/l steadily,
> nitrate about 50-60 mg/l (this is down from prior 100
> mg/l--when I added 
> no ferts, it ran about 12 mg/l routinely).
> phosphate 1.5 - 2.0 mg/l, probably closer to 2 (up from
> prior .5 - .67 mg/l)
> iron test showed over 1 mg/l, more like 2 mg/l, which I
> understand is high.
> I found tap was running GH 4-5, generally around pH 7.0
> -7.2.
> Before this test, as I saw the BGA, I had been adding
> some extra 
> nitrates +  traces, and stopped when I got these results.
> In the last month, at water changes I just added some
> dolomitic lime to 
> tapwater to maintain CO2/hardness, and stopped adding
> anything in the 
> last couple of weeks.
> Also had to drop the light levels, as one of my fixtures
> ground-faulted 
> (bye-bye!)
> So now I'm running two 92 watt CF 36" bulbs, on estimated
> 78 gallons 
> actual (at a guess, as it's both deep and a
> corner-diamond shape, and I 
> didn't measure on first fill, dummy me--90 gallons
> nominal) so that puts 
> it in that awkward 2 watts per gallon range,  I find the
> high-light 
> plants don't like it.
> I'm debating about how to punch more light down into the
> 24" depth with 
> some sort of fixture in less than 24" width.
> As always, thanks for everybody's help!!
> Heather

* * * * * * * * * * *
Coming Soon in November, the winners and all the other beautiful entries in the 6th Annual International Aquascaping Contest. Every continent is represented -- except Antarctica. Maybe next year Antarctica, too ;-)

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