WELCOME TO AA!!
Please do not cycle with live animals.
I bought a 55G at an auction that was a FW
tank. I cleaned it with CLR. I haven't had any problems. I rinsed A LOT and let it ait out for a week or so. I wouldn't recommend this to anyone, but I was new at the time. Just rinse, rinse and rinse.
looks like this is in it:
Citric acid 000077-92-9 <3.0
Hydroxyacetic acid 000079-14-1 <10.0
Sulfamic acid 005329-14-6 <7.5
No real metals, like copper, so you should be safe. Hopefully others will be of more assistance....