My aquarium is reasonably free of algae. However, the chain swords in the
foreground tend to get black spot algae more so than the other plants. Its a
fairly minor problem, however I am wondering if its avoidable.

Generally, I have only a bit of green spot algae on the front glass by the end
of the week; most all plants are pretty much algae free, with the exception of
the chain swords. The Valisneria can also get some black dot algae too.


Has anyone had experience with this issue? Is this a nutrient problem? My tank
tends to be on the low side in Nitrate, but I believe all other nutrients are
in line with recommendations.

Some numbers:

Nitrate levels: 2-5 ppm (I currently do not supplement Nitrate-- 2 ppm after
water change, 5 ppm by the end of the week.)
Potassium: ~1ppm (I add potassium twice a week)
CO2 injection: I keep the PH at 6.7 or so, my KH is 3.5 - 4.0
Iron: .1 ppm, fairly consistently

My tank is 135 gallons, and I add 25 - 50 ML of TMG twice a week.

Lighting: 385 watts, CF lighting, 12 hours per day. (Three 55 watt lamps &
reflectors from AH supply, two 110 watt fixtures made by All-glass.)

Substrate: 100% Fluorite (I do not add any type of substrate fertilizer.)

I change approximately 40% to 50% of my water every weekend, and use an Eheim
2028 canister filter.

Any ideas here? Are chain swords prone to black spot algae? -Bruce