Join Date: Jun 2015
Location: Victoria, BC, Canada
Depends on what you're keeping in the tank. Like the others have said it will increase the hardness.
What some forum members have advocated with rocks is to test it out in a bucket. Can probably do the same with sea shells, etc. add water to bucket, leave out overnight, test pH, GH, KH. Add shells, wait a few days and re-test. Wait a few more days, and test again. If you are able, use similar amount of water in bucket as in tank you want to put your shells in (or go for a similar proportion of shell to water).
Daisy Mae V
According to my husband, I have a habit of jumping right in!