Large gravel or stones are ok as long as they are not small enough to be swallowed. I can't see how that can be a comfortable substrate though.
My old boss at the MoS used to say, if you can't smell the chlorine, then you don't need to treat for it. I have also observed bullfrogs and green frogs hanging out in my pool even though there is chlorine in it. The green frogs were even calling. So if the chlorine levels are low enough it shouldn't be a problem. One should, however, err on the side of caution and treat tap water for chlorine/chlorimine.





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. on german pages they usually just mention calcium carbonate (which I do "remove") and now I wonder: is it because of different water qualities or because of different opinions (since there are also HUGE differences concerning the recommended tank size)?
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