Definitely can see a bit of concern. I have seen more than one pic with a cat taking a dunk from hanging out, on, jumping from, trying to get in, the top of an aquarium.
Would a wood "plank" work. Across the top front. I think that tank is 36" across. So like plus 2 inches on each side, with a lip over the edge, leave a gap for where the light goes and add an additional plank to the rear and maybe connect them across the top where the light would go.
So you would have somewhat of a walkway for the cats, since they will likely want to go across there anyway.
Lift up and off when doing maintenance. Just paint black.
A simple idea might be 4 legs of any favored decor style, strong enough to support said cat(s) with a "shelf" / cover, top, similar to a over toilet shelf idea, but over tank "shelf".
The top would sit above the lights and tank and leave enough space for cooling of light/ airflow.
You could make it where you lift off the "top", or a nested design where you can pull the top nest piece out to do maintenance.
Or, it might be possible to find a stainless steel, chrome or black kitchen / utility / storage rack in the right size. Depends on your location and whether you need something utilitarian or more stylish. There are DIY things which are wood and just sit over the wire parts to look nicer.