Does your tank contain crystals and/or rocks ? (sea shells etc, and anything else relevant)
Are they simply for effect or water chemestry ?

Can we start a list of rocks that are good for 'Tweeking' water chemestry and taboo rocks and crystals to avoid putting into any tanks..

I read somewhere that a slightly 'harder' water is prefered by some keepers to counter the usual suspect diseases, any thoughts?