No, reptile tanks are NOT the same as fish tanks. Aside from the differences in silicone strength, there is the fact that, especially if it was used as a snake tank, the residues can be extremely toxic to fish. I used a 20gH that was once a snake tank and I ended up losing almost 70% of the fish I had in the tank. My water parameters were constant at 0, 0, 20 (except for small spikes when a fish would die). The only explanation was that it had to be something with the tank. After doing some research, I found out that reptile tanks can be toxic when used for fish, even when washed with bleach (which I never do...I use white vinegar).