GardenBanter.co.uk - View Single Post - Arm & Hammer and green-water

20-11-2004, 09:57 PM

(Nick Wise) wrote in message om...
(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.

One thing I omitted in my description is that the canister filter
running on the tank is large and was purchased wet and mature second
hand.

Since I posted this message, I tested my nitrogens: ammonia and
nitrate were both nil.

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.

I've also got Ludwigia, Elodea, Bacopa, and Baby's tears. OOps,
forgot to mention these, too. At any rate, all plants in the tank,
without exception, have really done remarkably well. This is
consistent with the very low nitrogens I saw by testing (assuming that
my fish and BBS have been supplying nitrogen to the tank).

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.

I think the plants already have! :-)

So, you must figure
out why the plants are not absorbing the nitrates.

None present. I actually ended up *dosing* nitrates, as well as K.

There must be some limiting factor holding the plants back.

Turns out there's a big P spike in the water, and (initially) low N.
Basically the classic greenwater scenario, from what I can tell.

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 plants have all been kicking butt. I did, however, purchase a
phosphate test kit. Result? Phosphate almost off the chart! As a
result I've made a biggish change using reconstituted RO water, and
have dosed N and K.

The most obvious limitation on your system is CO2.

Hrm, I would have said it was the near total absence of NO3/NH3.

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.

[co2] = 3 * (KH) * 10 ^ (7-pH), right?

I've already dosed N and K. The plants are pearling noticeably more
than just before I dosed. Of course, the green water gets greener
(even now, with phosphate much reduced by waterchanges) but I'm
patient enough to let the plants just win out in the end.

I tried to dial in KH and pH for 20ppm CO2 initially by design. May
up KH to target 25ppm, though it's close to a purported danger zone
(for fish) at 30ppm.

[snip]

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.

Wow, 5ppm? Maybe you mean 0.5 ppm? Sundry sources (easily findable
within The Krib or plantedtank.net) speak of maintaining phosphate
1ppm. The tapwater here comes out of the pipes at 3+ ppm of
phosphate, commonly cited as a problem by local aquarists.

Not to say one cannot make it work on 5ppm. I'd imagine it's possible
so long as you keep something else, needed by greenwater and easily
competed-for by plants, at limiting concentration. Or you could UV
sterilize.

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

Not in my experience.

I've since called the mfr, and have done my own phosphate testing.
Result of both is consistent with posters' experience of A&H bicarb
being okay.

(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.

The corollary of this is that where there's some potentially excessive
amount of phosphate lurking, and where you have lots of higher plants,
you can run into green water in a hurry. Hm. Interesting, never
thought of it that way.

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.

Seems to be the conventional wisdom, yeah. If you optimize for
plants, they just beat the greenwater at its own game.

(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%

A good idea. Unfortunately, I have only 1 5-gal bucket in which to
make my change water, and the RO unit takes a coupla hrs to fill it.
10gal daily is about all I have time for, though yesterday I did more.

(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.

I think I'll stay the course for now, and just let the plants and my
smaller waterchanges converge to phosphate limitation. However, if
this fails then the blanket treatment isn't out of the question.

Nick Wise

--Trapper, in NYC where it's dark and rainy.