(Trapper) wrote in message . com...
Hi folks,

In the last 24 hrs, I have seen what appears to be green water in my
75 gal planted tank.

The setup is 2 weeks old, and pretty heavily planted as per
conventional wisdom. All plants are thriving, spraying out new
leaves, roots, etc. Amazon swords are producing daughter plants,
yadda yadda. It's mesmerizing to watch, actually. Fish load is 9
tetras, otos, sae, fed lightly 2x/day on BBS. Substrate is 100%
flourite. Otos are pooping and presumably not starving.

Problem #1: The setup is less than 2 weeks old? The tank has not
cycled yet. There is not a sufficient bacterial colony to remove
waste. The plants will remove a great deal of the excess nitrates and
ammonia, however, it does depend upon the plants. Stem plants are
best for this because they get nutrients from the water column. The
only plants you mentioned are, amazon swords, eleocharis, and chain
swords, all of which are heavy root feeders and do not remove a great
deal from the water itself. So without an established biofilter,
there will be a build up of excess nitrates, which will always result
in green water.

How can this be dealt with? The best way to deal with this is
somewhat counter-intuitive. It's not that you need to remove the
nitrates, you want the plants to do this for you. So, you must figure
out why the plants are not absorbing the nitrates. There must be some
limiting factor holding the plants back.

Algae:
green spot on glass, no biggee;
some sparse spots of brown on Eleocharis, and one chain sword. Rubs
off easily.

Water:
KH 2
GH 2-3
pH 6.50-6.60, CO2-injected
Temp: 77-80
Ammonia: nonreactive
Nitrate, Nitrite: not tested
Phosphate, Fe: not tested
Seachem "flourish" added on day 1 of tank's planted life, and again 2
days ago.
5-10 gal water change every couple days.

Problem #2: Or really just #1 part 2: You can worry about testing all
that stuff if you want, but the best way to tell is to watch your
plants. I see you have a lot of light over your tank. This will
really drive your plants to grow at high rates. Therefor, absorb
nutrients at high rates. The minute they run out of one, they will
stop, and then algae has a toe-hold.

The most obvious limitation on your system is CO2. With a PH of 6.5
and a KH of 2, you have around 18 ppm of CO2. I suggest adding more
baking soda to obtain a KH of around 3, then upping CO2 injection to
maintain the 6.5ph. This will give you around 25 ppm. You need the
higher rate to keep up with your lighting. After this, you will most
likely need to supplement N and K, the best way of doing this is with
Potassium Nitrate. Try this link for help in calculating how much to
dose.

http://www.csd.net/~cgadd/aqua/art_p...osage_calc.htm

Light:
10-12 hrs x 260 Watt dual 6700/10,000 compact fluor.

I stopped using Kent KH+ reagent ($8/bottle, doesn't last too long)
and began using Arm&Hammer bicarb to prepare my change-water (which is
either tap or RO water as time/patience allow).

Yesterday the tank had what seemed to be a greenish tint, which I took
to be (you guessed it) green-water. I chalked this up to having too
many nutrients, and have since changed about 25 of the tank's ~60gals
of water.

The changewater (some of which was RO, some of which was tap) I
prepared with baking soda. In other words, my operating assumption is
that the greenwater bloom was because of having added a second
Flourish dose before the plants ate all the first, and not because
there's, say, a phosphate contaminant in my baking soda or because
there's a nutrient spike in my tapwater. Until yesterday, no
greenwater was present in the tank, and I often changed with prepared
tapwater.

One of the best ways to get rid of green water is with a blackout.
Turn off all lights and cover your tank for 3-4 days. Do 50% water
changes every day to get rid of the excess nutrients. After this, the
green water will be put in check, then you must do what I said
earlier. You must get your nutrients balanced. Remember: HEALTHY
PLANTS WILL OUTCOMPETE ALGAE EVERY TIME!!

QUESTIONS PRESENTED:
(0) Should I be interested in phosphate, to the point of getting a
test kit?

No. Just make sure you don't run out. I typically dose enough for
5ppm every week with my water changes.

(1) Are there known problems with phosphate contamination of
Arm&Hammer baking soda?

Not in my experience.

(2) What is the lag time between establishment of
green-water-friendly water conditions and the appearance of green
water?

Can be very quick. Like less than a day.

PRELIMINARY ACTION:
(1) Suspension of fert addition until the green water goes away.

It's not the addition that's the prob, its the lack of optimum
conditions for your plants.

(2) Continuing 5-10 gal daily water changes until green water goes
away (where changewater is RO adjusted for GH and KH, maybe with some
small amt of tap added for traces).

Up this to at least 25%-50%

(3) Reduction of photoperiod to 10 hrs from 12.

Shut them completely off and cover with a blanket for 3-4 days. Your
fish will be fine, just feed them like normal. Your plants will be
fine also.

--Trapper, in NYC where it's bright and sunny.

Nick Wise

P.S. In the future I would post any plant/algae related questions to
rec.aquaria.freshwater.plants