Substrate 4 Axolotls

[Herbp]

l have recently aquired some axolotls 1albino 1"wild type" (both male) I call them ying and yang. I have them now in an enclosure I have created with a massive wet dry filter and no substrate. They have some large rocks to hide under and fixtures in the aquarium for cover, but I am scared to death to put anything in there that they might swallow or which might prevent them from recieveing the food (pellit food) which they eat like gangbusters.I am planning to set up a much larger enclosure for them but I would like to know... ?
Is it alright to use sand?
If not, what size gravel is ok?

 

[SludgeMunkey]

Here is everything you never wanted to know about aquatic substrates.

And here is everything you could ever want to know about axolotls and their housing.

 

[Herbp]

Sludge Munkey,
Thank you for the websites, I think I will go with the tile or large river rock. Although, I think the tile would work esiest for feeding purposes I will try to post some pictures once I have the tiles cut to see what you think. Thanks again.