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

S. Hieber wrote:

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

I'd like to hear more about how to keep them, too.

Currently got BGA in my tank (bleahh!) and yet fairly high N going, so I
suspect that I let my tank's TDS get too high, not enough water changes, for

How high is high? Also, what are the phoshpate levels?

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!!

If the nitrates are high but the phosphates are remaining
at about 1 ppm, continue dosing the phosphates but let lay
off on the nitrates until the level gets down closer to
about 10 ppm. Each 50% water change should cut the nitrate
level in half. It might then build or decline between water
changes depending on feeding and dosing.

Some have said bga occurs due to nitrate limitation. I've
seen it when the nitrates are very high. This could be due
to a combination of related factors, such as not enough
other nutrients for the plants to be able to use up the

Anyhow, try to aim for the targets and see if things don't
clear up that way. OF course, physcally remove what bga or
algae you can before a water change is always a big help.

good luck, good fun, sh

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