As some of you may remember, I have the following set-up...

75 gal. tank
220 watts of CF lighting suspended about 3-4" above the water line
UV Sterilizer
CO2 injected via pressurized bottle
KH 3-4 ppm
GH 5 ppm
pH 6.5
Temp. 75 degrees F
Nitrates around 6-11 ppm fairly steadily
Phosphates are around 0.1 ppm
I also add trace elements, etc.

I don't have any algae besides the normal "non-problematic" algae such as the spot algae on the glass from time to time.

The question I have is on Fe uptake. I was wondering how much Fe plants can use over the course of a day or two. I seem to be adding a lot of trace elements, and the Fe seems to disappear almost within a day. I've been trying to measure the amount in the water to get a general idea, but I can't register any a day after I've added some. I've been putting anywhere from 1/4 to 1/2 tsp. of dry trace mixture into a milk jug of water and dumping the entire mixture in.

I've heard two different sides of the UV sterilizer issue, and have a hard time believing it would corrupt the traces that quick. The trace mix (dry form) is about 2 years old, and I wonder if that is playing a part. Maybe the test kit is bad, although this doesn't seem to be the case since it will measure it one day but not the next. The plants are doing ok, but growth seems like it could be better (I've seen better in previous tanks). I have a hard time getting the robust growth without the leaves getting full of some minor spot algae. The Bacopa Carolinia seems to be growing slow as well.

Any ideas on this?

Thanks,

--
Craig Brye
University of Phoenix Online