Bit hard to tell from the pics if it ran down into the front panel or not. That will determine the extent of repair work. If it didnt travel into the front panel ur very lucky and face a pretty easy/minimal repair. If it did run into the front panel you need to drill through the crack on end to stop it from running any further. After u drill with around a 1/4” bit you can patch over and reinforce the area. If you dont drill, the cracks can and will run under any patch work you do. Ive fixed top braces like that before just by drilling alone and running the tanks as normal. Its amazing a small hole will stop further damage. Pretty common place for them to crack at also from sharp corners/lid cutouts and people lifting the tank from the braces.
If u can make that the back of the tank theres not much worry of learning how to fix it. Its less worry some its above the water line also. Drilling out the cracks and not filling up to the brim solves ur problem. Any patch work depends on how much u want to spend basically. Looks like 1 patch should do it tho. Most acrylic shops offer scraps for cheap. Your gonna want to use a 2 part glue called weld-on #40 or a solvent glue weld-on #3 or #4.
You can patch inside the tank, outside… or both. Id do 1 large patch up under the top sheet that fixes the brace and also catches/covers the crack into the front panel with #40. You have to flip the tank to do so tho as 40 is like syrup and runs until it cures. Id still probably flip the tank on its front face at a 45 degree angle with solvent also to prevent any glue running down ur front pane.
Inspect that crack closely… look for the points/ends and hit em with the drill. Acrylic is just like wood for the most part. Any pics dead on from the front? Or from the inside looking out? Kinda looks like it turned back and didnt run down the front
