Magnesium deficiency?

[Karnaaj]

I have had my planted tank set up for about 7 weeks now and I am pretty happy with it. However there are 1 or 2 species of crypts and 1 species of anubias that have light green leaves with dark green veins. They are growing and reproducing, just not at the same pace all the other plants are including about 3 other species of crypts. I heard that this might indicate an Mg deficiency, correct? If not what might it be then?

[Obsidian]

Magnesium or also possibly iron deficiency.

[djlen]

Give us some parameters on your water. Especially your hardness and pH, but as much info. as possible.
Tank size and fish population, and also what else are you dosing? CO2?

Len

[Karnaaj]

Tank size is a 65g. Ph runs right at 7.4 to 7.6. The tank has 16 fish none of which exceed 2". I keep my nitrates as close to 10 ppm as possible and my phosphates at 1 ppm. I don't have a hardness test kit as of yet but I can tell you that the water is very hard. I do a 25% water change once a week. I do not supplement CO2 but I do use Flourish Excel on a daily basis. Lighting is 192w of CP fluorescent, half at 6700k half at 10,000k. The substrate is 40 lbs. of fluorite on top of a very thin layer of ground peat. I have ~ 60 lbs of red flint gravel on top of the fluorite. There is probably in excess of 100 plants in there now, mostly crypts with some anubias and chain swords. No stem plants as of yet.

I thought about iron possibly being the problem because I don't know if the fluorite has begun leaching yet. I can look up underneath the tank and it looks like most of the peat is still there.

[tmorr37]

Q: I've been using Flourish Excel for the 4 days, and I've noticed that my Anacharis seems to be dying, while my other plants are doing fine. Why is this?

A: Anacharis is a particularly sensitive species (known to be sensitive to high temperature, trace copper, formaldehyde etc.). It is also sensitive to Flourish Excel. If you have Anacharis in an aquarium in which you are dosing Flourish Excel we recommend using Flourish Excel every other day rathter than daily.

[Karnaaj]

Fortunately I have no anacharis. Not one of my favorite plants anyway.

[djlen]

Injecting CO2 would be a better option generally, but even more helpful in a tank that large.
I would get a kH/gH test kit to see what your water's hardness levels are.
Your N/P ratio is good. If you don't dose traces, I suggest you pick up some Flourish(not 'Flourish Trace') at the LFS, and dose it regularly. You will probably see an increase in growth and nicer colors, especially of your Crypts. They like their traces.
And even better option would be to order some Plantex Trace from Gregg Watson. Much cheaper to use for a larger tank like yours.

Len

[Faramir]

If the water's hard it's unlikely that there's a magnesium deficiency.