Why do you buy your water at a petstore?
What kind of wAter is it?
Can you post some pictures of the tank?
What are the water parameters? Ammonia nitrite nitrate and ph?
What kind of filter are you using? How big of a tank and how many axolotls
Dechlorinated tap water is probably the best water you can use for an axolotl unless there is a reason to why you cant use your tap water. Seems like a waste of money for water when you should be doing quite a bit of water changes
Is your tank cycled? Well i guess i could figure that out from water parameters.
You should always have enough water to do daily water changes if you have to because if you cant id really suggest you taking your lotls out of the tank doing 100%water changes in a tuperware container to make surw they are in fresh clean water. So regardless you should have water..
Do you have sand in your tank?
Please answer all these quesfions for us to better aid you
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it really is important for the welfare of your lotl because it can be many things from a simple bacterial bloom to your filter malfunctioning and leaking toxins to maybe an uncycled tank and the water is dirty etc.. So it is very important!
I would really suggest testing the water before starting wTer changes. 10%may not be enough to keep the levels low enough for an lotl. I suggest 20% daily unless your levels are off the chart then maybe a bit bigger. The larger the water changes the longer it will take to cycle but
You have to put into account the welfare of your lotl. Also a test kit is a must to have expecially if you are cycling with your axolotl since the spikes can kill your axolotl if not properly watched.