I was reading on the internet that you should not use limestone in a planted tank. I have had it in my tank since day one and I was just wondering exactly what the limestone does and if I should take it out immediately?
It'll dissolve (slowly) into your tank, increasing your alkalinity and driving up your pH. If your not having a problem with it, I wouldn't worry about it.
Limestone is fine in a fish tank, especially if you want the additional alkalinity. If you don't, it may cause problems. If its causing problems, yank it.