Question About Aquarium Rock.

[LolaLouie]

I just bought a rock for my aquarium from a fish shop but have read that some rock is unsuitable as it changes the pH of water.

The rock I bought I believe contains calcium as it bubbled when i washed it in aquarium water. It was labelled as "rainbow rock" (have googled it and looks like it was labelled correctly but can't find much info on it). It has been in my tank for 2 days now.

My tap water is very alkaline (8-8.5) and most my fish are ones which prefer slightly more acidic conditions.

I just tested my pH after reading about the rock and it has gone down to 7.5.

Does this rock make water more acidic or more alkaline?

Is it ok to leave the rock if I want a lower pH anyway?

Thanks

Gemma

 

[radioman]

one way to test if a rock is safe is to put vinegar on it. if the vinegar bubbles it contains calcium which i believe lowers the ph but I might be confused if it lowers or raises it so check with another member. if it does have calcium i would not put it into the tank.

 

[Matt_northants]

As the rock reacts with vinegar, which is a weak solution of acetic acid, then it is made up from a basic material, most probably a form of calcium carbonate. This means when placed into water it will increase the KH and the alkalinity. When was the last time you checked your tanks pH before adding the rock? How long has the tank been set up? Do you perform regular water changes and clean your substrate? As tanks age they have a predeposition to lower in KH and become more acid due to the processes by which the fish waste is broken down.