Help me raise the PH in my planted tank

I am not sure what color scheme your tank uses or what other structures you have but I use Texas Holey Rock to increase my pH (can be found on ebay). Then again I live in Texas so it is easy to find. Basically it is limestone rock. Works great at naturally increasing the pH.

any limestone base rock will do, or sea shells, or u can buy crushed coral substrate to mix in with ur exsisting substrate, or another simple and very effective way to raise ur ph without chemicals or in a manner u can reverse rather easily if need be is to increase the areation of your tank. the more dissolved oxygen in the water the higher the ph will be. this may not be the best for ur plants though. i only run my airstone at night when my O2 level may drop and my plants seem to do fine.

Magnesium and calcium are two nutrients that plants will take up that would lower the buffering and thus the ph. If your tap water has low buffering to begin with you may need to add a little of those two elements to your water when you change it. Epsom salts, found in the pharmacy section, has magnisium in it and is what I use to provide that.

I would suggest you find a way to add some in if you are low as to little magnesium can be detrimental to your fish health.

what exactly are is your ph now, and what was it before? the fish may react to the sudden change, but if it only changes that one time and then stays stable, you shouldn't need to worry, depending on the actual numbers.