cement for DIY rocks

[Starry]

use type 10 cement. Water softner salt is better anyhow, its cleaner. Also always available.

The mix I used was 1 part cement to 3 parts "other" other being salt, sand OS ect. With mine I used 2 parts salt, 1 part Caribsea seaflor special grade sand (cause I had some). And 1 part type 10 cement.

I just put my first piece in my sump about 2 weeks ago and today I noticed a few spots of coraline on it.