problem with crypts

[guppygirl]

Hi all,
I'm sort of stumped with my cryptocoryne. I just added more light, (130 watts) and they seem to be doing worse! There's a line of black algae around the edges of the leaves, but not on the middle. I know they're low light plants, but what does this mean?
Thanks,
Robin

 

[George Farmer]

Some Crypts are sensitive to sudden changes in their environment, especially pH change. I can only assume the extra light is causing your problems. More light equals more oxygen from your other plants, too much oxygen can cause your pH to raise. At least they're not rotting away (I hope), hopefully they'll adjust to your new light. Have you tried adding more co2 to keep everything in balance? Adding more light without compensating with other nutrients may result in an algae break out.

HTH