Something amiss in my 90g high tech

[chris_todd]

In my 90g high tech tank (plenty of light and CO2, mineralized soil under flourite, but no dosing as of yet), the Limnophila aromatica I got at Aquafest looked great at first, with amazing purplish undersides, very much like the pictures on the APC plantfinder.

But lately, the upper leaves have been coming in almost white. Any idea what kind of deficiency (or excess) this might be caused by? The APC plantfinder says the best colors come from Nitrate limitation or Phosphate excess - may I infer that I have high nitrates and/or low phosphates? (I'll do water tests later tonight, though I'm not sure I trust my test kits).

On a possibly related note, I've noticed recently that an oily film has developed on the water surface, and I've read in a few places that it might be related to phosphates (though the suggestion was it was due to high phosphates, as if from the breakdown of excessive feeding or fish carcasses decomposing). I have been feeding the Discus frozen bloodworms and mysis shrimp, but only using cone feeders.

I've also noticed the leaves of one (but only one) of the red flame swords has undulating edges on the larger leaves (which are getting really massive!).

I also have a good bit of algae (some kind of hair algae as well as green dust on the glass), but I had attributed that to the new tank algae breakout that I seem to get with every tank, and which usually clears up in a month or three. It has started to abate now that I do a 3 hour noon burst with all four bulbs, but only have 2 bulbs on for most of the day. I don't have much of an algae crew in there yet, just some pond snails.

Any thoughts or suggestions? Something is amiss with the tank, but I'm just not sure yet.

[ingg]

My first guess'd be iron from new growth being white honestly.

[chris_todd]

Well, I just did a bunch of tests with my API test kits, as well as the Red Sea "plant lab" Iron and CO2 test kits. pH, temp, and conductivity were measured with my Hanna combo meter, in mid afternoon just after the noontime light burst was over. Here are the results:
pH 7.31
temp 26.2* C
conductivity 543 uS/cm
My CO2 drop checker has been a darkish green color for several days
KH 6.5
GH 10
NH4 0
NO2 0
NO3 about 10 ppm
PO4 about 1.0 ppm
Ca++ about 60 ppm
Fe 0 (at least there was no color change with the test kit)
CO2 about 14ppm

So it looks like the plantfinder (and Dave) are correct, assuming my test kits are believable - there's no detectable Iron in the water column, nitrates are moderately high and phosphates appear low. From the plantfinder:
"Iron is especially important for good coloration and growth. A rich substrate will accelerate growth, as this species often develops a substantial root system. Nitrate limitation or phosphate excess usually produces the most pleasing colors." So there you go - yay PlantFinder!

It also appears that my CO2 levels are a bit low - about 10 ppm based on the KH/pH relationship, and about 14 ppm measured with my test kit, despite the fact I was running about 4 bubbles per second. So I'm cranking it up to about 6 bubbles per second. I have BBA growing on the Cyperus helferi (and only on the helferi), and I've read that BBA is a sign of too low CO2 levels. I'm also doing a water change, after which I will dose Flourish Iron.

Actually, now that I think about it, are 10ppm Nitrates considered high and 1.0 ppm Phosphate considered low?

One thing I don't understand - my tap water is KH 4 and GH 8, but this tank has KH 6.5 and GH 10 - how is it that these values could be higher in a heavily planted tank? I would have thought they would go down as minerals are absorbed by the plants. Could this be minerals leaching from the mineralized soil substrate? (note that before I put in the soil, I put in clay, dolomite, and potash, as described in the mineralized soil article) Thoughts anyone?

[ddavila06]

i used to have that oily nasty looking film on the top for a while, i had to get a surface skimmer and keep it with my canister filter for several months, then i took it out and didn't come back. do you have any surface aggitation (powerhead, HOB filter?) i have the hydors moving top water towards the bottom now...might help

BTW, still have the surface skimmer if you need it.

[ddavila06]

found the link to the oily thing : http://gwapa.org/forum/viewtopic.php?t=3101&start=0

[Aaron]

Potassium would be my guess. That soil is old enough where the original potash is likely gone. Try dosing just 0.5 ppm of potassium daily and see what happens.