Adding additional pebbles to 20 gallon freshwater tank

[Perbud]

Hi All..I’m thinking of adding more substrate to bring it up to 3 inches in my existing tank.Since the initial layer is about 1 inch of natural pebbles is it safe to add new identical natural pebbles to the old 1 inch layer?

 

[Colin_T]

Yes it's perfectly safe and fine to do. Just wash the new gravel under tap water and when it's clean, add a handful at a time to the tank. Start at one side and careful spread it over the existing gravel.