Black flourite sand

I'm finally getting an axoltol, so before I put him in the tank I want to make sure I have everything perfectly set up. I have a 40 breeder that's been seeded and is just about done cycling. But for the moment I plan on putting the axolotl in my ten gallon that used to be a planted tank and is totally cycled and packed with plants. I would like to keep him in the ten gallon because I'm gonna have to travel with him for christmas, and it's much easier to take a ten gallon somewhere then a 40 breeder. The only problem is the substrate is black flourite sand and I remember reading somewhere that it wasn't healthy for them. Is this true?
Also I have a marineland c220 canister filter in the ten gallon. Is that fine to leave in? A betta fish used to occupy the tank and it got pushed around in some areas, but the majority of the time it did just fine.

From what I've gathered the only straight forward answer to why black flourite sand is bad is becuase it add's extra iron to the water, which may cause problems in the long run. Honestly I think I'm going to skip the ten gallon tank, and just move it straight to the 40. But just out of curiosity does anyone have any other reasons for not using flourite in salamander tanks besides iron? Someone posted that it may add unbalanced ph swings, and algae blooms, however I've never noticed either while using the substrate