Does red slate create a red residue in fish tanks?

Answer 1

You betcha! The various minerals, chemicals, etc. that are in water will slowly break down rocks and cause them to leech into the water. Slate is especially soft and will break down very quickly. Leeching rocks not only can add color to the water and substrate, but also affect the ph levels.

Answer 2

The red residue may be a type of algea. If the algea is not green it's not good. Don't think slate breaks down like that in water.