" wrote in message
om...
You are not going to beat the algae through nutrient limitation, you
can try and you can try.
Yes. You are preaching to the converted :-) By the time that nutrients
are so low that algae won't grow anymore, the plants will be long dead
and, in the process of decaying, produce more nutrients for the algae ;-)
Black brush algae (the bane that caused me to tear down
my tank eventually and start again) and, to a lesser extent, beard/staghorn
and green thread algae.
Ahh well, here's your issue:
CO2.
Directly poor to variations of good to low CO2 levels is a great way
to culture BBA.
Poor CO2 is 90% of all algal issues for folks using CO2 gas.
I can believe that. I had ongoing problems with my CO2 system
(leaks, stuck needle valve, losing calibration on the probe, etc.) So,
when it came to widely fluctuating CO2 levels, I was your man.
I've since replaced the CO2 system with something decent, so that
part of the equation is well and truly under control now. (BTW, if anyone
is looking to buy a CO2 system, stay clear of the Eheim one -- it's
rubbish.)
Keep the CO2 20-30ppm during the entire lighting peroid, check pH at
night(PM) and in the early AM. Make sure the CO2 is good during both
these high/low points.
I have 4 degrees KH, and the CO2 system is set to a pH of 6.8. The
hysteresis on the controller is 0.1 degrees, so the actual value fluctuates
between 6.75 and 6.85. (The manufacturer says that the probe is accurate
to 0.01 degrees after calibration.) Looking at the CO2 chart at
http://www.thekrib.com/Plants/CO2/kh-ph-co2-chart.html, I guess I could
change the set point down to 6.75 without getting more than 30ppm. I might
just do that. (In fact, I'll do just about anything to keep BBA away...)
Yes, seems that way. The Redfield ratio indicates that high phosphate and
low nitrate favours BGA, and high nitrate and low phosphate favours
green algae. (This agrees with my previous experiences -- I was battling
green algae until I picked up on your recommendation to dose phosphate.
Unfortunately, by the time I saw the truth, it was a bit too late to save
the
tank.)
Well here's what happened with your tank:
You added PO4, this drove the NO3 uptake rate faster, so the NO23
dropped to zero and the plants growth slowed down significantly. BGA
appeared.
Actually, no. I kept dosing NO3 as well, and kept it in the 10ppm range.
But, by the time I started that, the brush algae were already too well
established to get rid of again (and I still had the problems with the old
CO2 system).
I've just (a week ago) set up the new incarnation of my tank. (150gal
nominal,
actual water content 130gal.) I've been following your posts on APD about
whether to fertilize a freshly set up tank and started dosing KH2PO4 and
KNO3 from day one as you recommend. So far, things are looking good.
I'd do this:
COP2, then check it again and again till you go nuts and geel very
comfy with it being 30ppm or so.
Generally in 99.99% of all cases, the CO2 will appear lower than the
actual concentration if there is an errorin testing or some other
acid, stray current in the water.
Well, I can determine KH to an accuracy of +-0.5 degrees, and I can
determine pH to an accuracy of +-0.01 degrees, so the error in CO2
levels is fairly small. I can certainly keep it in the 25-30ppm range
with confidence.
That is the first order of business anytime you see algae or have a
growth issue with plants.
Poor CO2 will get any and everyone from Amano down to the newbie, to
myself.
Well, my previous experiences seem to confirm this, so I will take your word
as the gospel on the matter ;-)
You can do the estimative index and not bother testing if you wish, or
you can control it and double check your estimations and find the
rates of uptake.
You can also use the plants themselves as indicators.
Eg Riccia pearling is great for CO2.
Right now, the phosphate is disappearing about as quickly as
I pour it in. Over four days, level dropped from 0.5ppm to
below 0.1ppm.just barely detectable with my test kit, below
less than 0.1ppm. Nitrate levels seem to be dropping less quickly,
from about 10ppm to about 6ppm over the same period. The
tank can't possibly have cycled yet, having set up for only a week,
so I guess things are still finding their balance. I'll keep measuring
and adjusting NO3 to around 10ppm and PO4 to around 0.5ppm
and see how things shape up (all the while keeping CO2
at 20-30ppm, course ;-)
Dose the macros and traces every other day alternating.
I've been using Duplaplant 24 every day at the suggested dosage.
Would you recommend dosing DP24 only every second day?
If you have moderate or lower light, you can do about 25-50% less
dosing.
No, it's fairly high light -- two 150W metal halides and two 36W
fluorescent tubes, for 10 hours per day. That comes to about
2.8W per gallon.
Biggest issue for now: CO2.
Definitely got it, thanks! :-)
Cheers,
Michi.
--
Michi Henning Ph: +61 4 1118-2700
ZeroC, Inc.
http://www.zeroc.com