I figured I would see what came up here before I put in my two cents worth...
I whole heartedly disagree with the "bare bottoms cause stress" theory. The only thing that causes axolotl stress is the keeper. Bright lighting, warm water, lousy husbandry practices and poor diet are among the most common causes of stress.
Myself, and many others have been keeping axolotls without a substrate for many, many years without issue. A bare bottom tank or a sold substrate tank (like slate or tile, or custom made fake rock) is best for this species in my opinion. The ease of keeping it clean is the most important aspect. An easy to clean tank gets cleaned more often. Properly maintained tanks tend to have good water chemistry. Here is a link to
everything you never wanted to know about aquatic substrates.
I feel the whole stress thing comes from poorly informed keepers and the tendency of the internet to spread invalid, unsubstantiated information quickly. Axolotls do not like light. They like it dim and dark. If there is light, they need lots of places to hide from it. I suspect many folks want to be able to see their pet(s) at all times, like most fish. truth be told, most caudates in general do not want to be seen unless you have nightvison goggles. This need to be able to see the animal all the time cause many folks to skimp out on proper hides. It often leads to overly bright lighting for far too many hours in a day. Sadly, thosde conditions make for very unsettled axolotls.
I am a huge advocate of bare bottom tanks for this species.In my experience, the healthiest axolotls always seem to be the ones with out substrates.
(Note, currently my axolotls are in a fully planted, river rock substrate tank I put together just to take pictures of a few months back. While I would prefer to put them back in a bare bottom tank, my wife really likes the "fancy" tank. It is a horrible, time consuming pain to keep properly cleaned.
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