I use tile because its cheap, lasts a long time, heats well, looks more natural than some other substrates, safe for my geckos, and very easy to clean.
The only downside i have noticed is tile also cools down very well, so if a bulb or uth goes out it will get releatively cold fast.
I prefer to use tap water because it is enriched with vital nutrients, but it also has the chance of having bad stuff in it too. It seems to be working just fine tho.
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One of my geckos constantly wants out and the other not so often. I usually take them out at least 1 time per day tho. :)
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check out my site http://reptileisle.webs.com