That’s a big no, you need to have the tank sitting on a flat surface. You have a good chance of tank failure with that. Looks like a pretty decent size tank and the plastic trim isn’t going to support the center .
it’s a 125 i built the stand but needed to jack it up some and didn’t think this was to bad but they say not to put anything going underneath the tank. but i thought if all 4 corners are flat and level it was good
It would be good to have more support in center of tank . Bit if the black trim is sitting flush on the stand all the way around the bottom you could get by. Center support is a plus but not 100% necessary.
I agree, you could make another 2x4 permitter that goes around the entire outside of the tank and screw it down to the existing one. I really like to put a piece of ply on top of the 2x4's and below the tank because the 2x4 joints are often not perfect, but if the joints are good it is not needed. Make sure it's flat and level and you should be fine. Another thing to consider is sheer strength, I see you have 4x4 uprights in that stand which is plenty strong, but I don't see anything that braces those at a 45 degree angle. If the stand wiggles at all it might be worth adding a support that way too.