Black spots on my sword plants

[wellmax49]

Hi, I live in Auckland New Zealand and have a 300 litre aqarium which has been in action now for nearly 18 months. The problem I have is my sword plants have developed black spots. Is there any remedy for this. Kind Regards. Wellmax

 

[JohnPaul]

Do the black spots develop to the point where they become holes (pinholes) in the leaf? If so, that sounds like a potassium deficiency. If they are just black spots that stay as black spots...hmm...I have no idea.

 

[DragonFish71]

Here's a link that helped me figure out some things with my plants. As JohnPaul said, it could be potassium or phosphate deficiency. There is also a black looking algae that "spots" leaves. This article calls it hard green dot algae. I'll see if I can find other info.

Algae control in the aquarium

Plant Deficiency Picture Diagram - Fertilizing - Aquatic Plant Central

 

[DragonFish71]

Freshwater Algae Types: An Illustrated Guide - Article at The Age of Aquariums - Tropical Fish

 

[Jason7894561230]

Mine doesnt have black spots?
I'm not sure