Additional water to 10g tank

Question
Hello

I have a 10g aquarium fish tank and the water is evaporating. I want to add water back to the top but I don't know how/what to add. I have KH/PH plus and nitrivec on the first day we bought the tank. So I was wondering if I could just add these into fresh tap water to the tank? Is it okay? Or do I just need dechlorinator?
Any suggestions would be great.

Answer
Hi Junwoo,

All you need to add back to the aquarium is water. Remember, "pure" water is what evaporated so anything else is still in the tank. The mineral content of the water, carbonate salts, aquarium salt (which is good to use in new setups, but I wouldn't use it once the tank is cycled), any fertilizers for live plants...all these things do not leave the tank when the water evaporates. That is why adding just tap water with dechlorinator to make it safe for fish, is all you need to do.

For small tanks like yours I find the 50 mL bottle of Prime works great. It has a dropper cap, making dosing super simple. 2 drops per gallon is all you need, unless you are registering ammonia or nitrite (then use a double dose to detoxify these; the instructions will be in the back of the bottle).

I hope that helps! Take care.
Nicole