lost 11 fish this morning can you help?

[chefkeith]

You can test GH immediately after a water change.

For future purposes, here's an article with some information about keeping clown loaches.
http://www.loaches.com/species-index/cl ... cracanthus.
The minimum tank size recommended here is 280 liters / 75 gallons.

Crushed coral or other calciferous rocks would cause the GH to rise. This can cause osmoregulation stress on the fish when water changes are done if the source water doesn't match the tank water. It will need to be removed if there is any.

One of the most difficult parts of keeping fish as pets is that we sometimes learn things at our fishes expense. I only wish you could had posted here a year or two earlier. Maybe then the nitrate problem could of been avoided.