As a newcomer to Goldfish keeping I am in the process of setting up
four tanks in an exterior building (see previous posts) .
I have now built my first small tank (25 gall) and all is fine (filled with water) and am nearly ready to
set up with decor etc. before "cycling". I intend a four tank set up with two 25 gall and when I
have cut my teeth on the smaller tanks I intend two further bigger tanks 50 gall+ in the future when I have
learned the pitfalls. My set up is in an exterior building to my house so appearance doesn't come into
the equation. I have made an easy syphon based empty system, just turn a tap and the tank empties outside into a water butt and refills by electric pump from a conditioned source of water, No syphon tubes, buckets,spills and floods,this making water changing so easy you could do it every day if needed.

Sorry for going on,my next question for you experts is "substrate"
Has any body used broken grey (roofing) slate as a substrate. Will this affect the water PH ??
Is it suitable or not, just something different. If not I shall revert to a shallow layer of gravel.

Advice always welcome.