if you're a bit handy at DIY it's not that hard to fix it, you basically peel the silicone off, remove the panel and silicone it back into place.
you buy aquarium specific silicone for the job for a few quid.
rabbut will be able to do a good write up of the process for you no doubt!
depends how much you trust your handywork though, can ruin your carpets if you get it wrong!
MW, my intent here is to politely object to "it's not that hard to fix it". I apologize in advance if anything I say appears harsh. Again that is not my intent.
IMO, "it's not that hard to fix it" is a subjective statement. I have, apparently successfully, resealed an old 22 gallon aquarium. I love that aquarium and am glad I did it. From that experience, and my experiences painting my house (I know this seems unrelated, I'll explain later), a successful reseal is time consuming and difficult. It won't stop my from doing it again. I just won't undertake it lightly as it is time consuming and IMO requires a respirator.
IMO, the success of any application of a liquid/paste that will be relied upon to harden and seal a surface is highly dependent upon preparation. If the underlying surface isn't dry, clean and stable, whatever is applied to will fail to seal sooner rather than later. Removing all of the old silicone and drying the joints will take time. The effort becomes harder the larger the aquarium. I estimate that surface prep on my 22 gallon was 10 hours. Removing the silicone happened in two phases, first was the intial removal which has to be done carefully to not scratch or crack the glass. Left behind were very thin and patchy layers of silicone that I could more feel than see. Finding and removing these took about 3 of that 10 hours. Then the surface has to be cleaned, not difficult but the surface has to be dry before applying the new silicone. I waited three days, keeping the tank in a heated room. Applying the silicone is a bit of a skill. One has to work quickly as the initial setting happens quickly and it need to be smoothed and pressed into place. This is where the respirator is important. The acidic gas burns. I started without the respirator and quickly regretted it. Then there is a seven day wait for the silicone to fully cure and then I tested the tank for seven days before relying on the seal to hold.
Maybe I am doing more work than is necessary but here is where my painting experience comes in. I get 10 years out of an exterior paint job. My neighbors get three. The difference is in the prep and application. I thoroughly clean and caulk the surface and then brush/roll the proper product(primer and paint). My neighbors pay a contractor who will maybe hose the surface and do some spot priming before spray painting with maybe a backroll. As I said, I get 10 years out of a paint job, they get three.
OP, don't be discouraged. Go for it. IMO though be prepared to do a thorough prep and definitely use a respirator when applying the silicone. On a 90 gallon tank, I would consider having a helper to apply the silicone, one to apply it with the other following and smoothing it. Practice the application on a smaller tank first. You don't have to do an interior seal. Practice on one of the back exterior seals so you have a feel for how fast the caulk cures and how messy the application and smoothing is. (I can be a bit anal and also sealed all of my exterior joints.
As I said, go for it. I am glad I resealed my 22. If I had the time, there is an 84 gallon locally that needs a resealed than can be had at a good price. I just don't have the time right now.
And definitely use a respirator when doing a large area of silicone.
Good luck. IMO, it is a lot of work but well worth it. Go for it.
If the waterproofing sealant is peeling, the structural stuff will be failing shortly after...
