Pepper, you're going to end up killing your Axolotls if you don't cycle your tank properly.
Read the Link that Casey provided, also visit this link:
www.axolotls.org
A properly cycled tank is a properly balanced environment for your Axolotls.
I would strongly suggest taking your Axolotls out of the tank and putting them in water safe containers with clean declorinated water with daily water changes until your tank has cycled. Gallon ice cream buckets or plastic food containers work well for this.
I had no idea about tank cycling when I first started, so thanks to this forum and the people here I learned a great deal and I am so glad that I did! You will too once you understand
If you need to get your water tested, take a water sample to the local pet store and they should test it for free.
After 30 days of tank cycling, the readings should be
Ammonia: 0
Nitrite: 0
Nitrate: 0.0 - 20
Ph of 7 - 8
Water temp: 63 - 75 degrees F. ( 17 - 24 degrees Celcius)Keeping Axolotls at higher temperatures stresses them, but as long as the temp doesn't go above 75 degrees then there shouldn't be any problems as long as you keep the tank clean.
25% water changes need to follow weekly with weekly tank cleaning, sand vacuumed, etc. Also remove any un-eaten food or waste as soon as you can to avoid changes in water quality. Only disturb the very top layer of sand when cleaning the tank. Good bacteria that provide Oxygen and eat the waste of the animals living in the tank live in the sand substrate. They start to colonize and are properly established after 30 days.
Gravel is also not a good idea to keep with your Axolols as they will eat it and get constipated, could get very sick or even die. Aquarium sand or bare tank bottoms are best. Even large gravel poses a threat to the little Axolotls.
Good safe brands of Declorinator are Amqual+ and Stress Coat. Stress coat is the better of the two and has Aloe in it to protect the slime coat on the Axolotls and also helps restore damaged slime coats.
I never heard of mixing aquarium carbon with gravel before. That doesn't sound right.
Also what are your tank measurements and what type of filter are you using?
Hey and Casey, you're doing pretty good with your info