Yea, Knew I left out some details. The 37 gal tank has been running for 42 days but the brown dusty diatoms have been noticed for the past 2 weeks. Pulled out the crypt and was able to brush the "brown dust" off the leaves, so I'm sure it's not algae per se, but diatoms. I only stopped the ferts today, so it could have been that.
I am using Flourite over Flora-Max substrate in the 37 and only Flourite in one of the "tens". Both these tanks are cycled and have brown algae "dust". The "ten" has been going for 54 days now and the crypt is growing great, but a few leaves are showing brown dust on them like the 37. So, there is a common thing happening here. I have since clipped the few leaves with the dust off with scissors and have increased the aeration some to create water movement and add O2, but I could still be using too much light on both tanks.
Do think the light is on too much thou, I agree, but diatoms grow with or without light I hear, perhaps this is wrong. Nitrites are 0.25 and ammonia is 0, nitrates are 0 also. The tank had zero nitrite at day 30, so it is cycled quite well. Don't as yet have a phosphate test kit. They're hard to locate in Florida. I'm ordering some stuff from the net soon and making up a list right now.
I do think this problem will just "cycle" itself away, from what I've read so far. I am optomistic about it. Years ago, I had all kinds of real algae and possibly even these diatom things too without even realizing it, and it never worried me. The tanks I had always cleared themselves, albeit with a little scrapping of the glass! Now, I have learned to do water changes and that may have stirred up the substrate some, causing or aggrivating the problem.
I will try to update this thread and see if I can pin down the offending "variable" to the diatoms.
Thank you for your help too!