Help to Identify Black plaque on plants
I have Aqueon 65 gal tank, 48"Wx 12"x 24" deep. It has natural gravel for substrate. I have had tank set up going on 3 years. It is a community tank of asst. tropical fish. I have attempted to grow a planted tank for a little over 2 years. Started with stock hood with LED strip and some Anubas and Swords, they grew alright at first then over time stopped growing then died back. The Anubas never have completely died, new growth comes out constantly just to have some type of black cover the tops of the leaves, then holes in the leaves till they die and fall off. I do not believe this is BBA as it has no hair type growth and feels like a hard scale to the touch. This also gets on all of the plants. See pictures. I have done so much reading here and other articles, and talked to LFS employees who gave multiple advice options, tested water for many problems they suspected and found no real issues. I have tried so many different approaches that honestly I am confused where I am at now.
Currently I have a Finnex 24/7 Planted 48 light, have had it for more than a year and have tried different lighting levels, intervals, and color mixes. At this time the remote has stopped working, so I am stuck at current settings. Before I replace it, I was hoping to get to the bottom of this and buy the proper lighting.
I am not interested in CO2 at this time, as not being able to grow even low light plants properly, I don't want to complicate things further. I have tried the whole regimen of Seachem liquid products, ( Flourish, Iron, Potassium, etc.) Tried Thrive for 1 bottle, then read it was for a heavily planted tank. Now I am using Thrive C, 2 pumps per week, and Flourish Excel dosing 2 times a week.
Ammonia, Ph, Nitrates, Nitrates always test good. Do about a 30% water change every 2 weeks. Fish very healthy. The only Algae issues I have is the green spot type on glass, has to be clean off every 4 -5 days.
I believe if I could find the cause of this black plaque that kills the plant leaves I may be on my way to success, but I have had issue with it for over 1.5 years. I have prunes, tried peroxide baths, it won't run off. The fact that is only on the top of the leaves I was thinking too much light, but having a 24" deep tank, my reading says that I need very bright light.
Any questions that I can answer, I will try. Any suggestions are welcome. Some of the reading has said that a deep aquarium need so bright light that CO2 is needed. Other have been successful without it.
Thanks for taking the time to read this post.