Yeah, it is fine. The ph drop from co2 won't affect your critters. It's the hardness differences going from a certain ph to another that they need to be acclimated for. The ph actually doesnt matter much within normal ranges. Osmotic pressure from dissolved solids is what critters need to adapt to (as i understand it anyways) and co2 won't affect that.
You do of course need to worry about having enough oxygen and not too much co2. Water changes will be helpful if you gas your fish.