New Axolotl Parent Question

Hi all, I got two axolotls last month, Charlie and Darwin. My dad and I were looking at a local petstore for more fish for my tank at college and saw these guys. I said I wanted one and my dad was like "yah ok get one" which is a big deal for my dad because I have a lot of pets at home and I'm "not allowed to get any more major pets until I have my own apartment." Charlie is "glow in the dark" yellowish and Darwin is white with "freckles" on his face. I'm studying zoology and am passing my axolotls off as fish at my college (we can only have fish). And I'm from Illinois.

So I have a question. They were in a tank full of gravel at the pet shop and when I got them Darwin pooped out one pebble, and Charlie regurgitated 3 large pebbles. It has been a month since this has happened. I was wondering if axolotls' organs can be blue or if the food in their stomachs can look blue. Darwin is a white axolotl and its abdomen shows a blue something inside of it and its stomach is as wide as its head but is more bulgy/round downwards. Darwin's stomach is smooth and not bumpy like when Charlie had many stones inside of him. He/she (I don't know what gender it is since it's still young) eats a lot and is very active (even eating one of Charlie's legs; they are in separate tanks now). They are in tanks with no substrate and I feed them blood worms.
Thanks for any information!

Was the pet shop gravel blue? the organs of pale axolotls (albino, luecistic) can be very noticeable when they're juveniles. From experience I've found some parts can look slighly blue, some slightly purple, brown..just dark, dull shades. If the area you're concerned about looks round or spherical, it could very well be gravel. Being as they are eating well and passing the gravel I wouldn't be too worried. If things take a turn for the worse fridging can aid passing: http://www.caudata.org/forum/f46-be...ick-axolotl/85263-axolotl-fridging-guide.html but hopefully this won't be necessary. I've known axolotls to continue to pass gravel for months after being taken "off" of it so it's not uncommon (un)fortunately. Juveniles quite often take chunks out of each other but again, it's usually nothing to worry about. You should be able to reintroduce them without a hitch in time.

Thanks for the advisement! Some of the gravel at the shop was blue (it was multicolored). I'll keep an eye on him. And I plan to re-introduce them once they're bigger and I have a larger tank.