Hello fellow MFK'ers,
thank you for your posts. Its not really easy to see this back. This is the first time I logged in since yesterday.
Why the tank cracked? I have no Idea. The tanks are 175x100x50cm(875 liters or around 250 gallon) and made of 10mm glas. (Shops will make these kind of tanks in 8mm thickness and the cheap shops 6mm). I made them 2 years ago, and were never moved. They also lay flat on a plywood board I glued them on(water resistant plywood), and these lay on a frame that should be more than strong enough to carry the tank.
The crack is right in the middle of one of the bottom plates and is a real star, not a crack like you usually see when a bottom splits due to stress.
The only thing I can think of is that while the pups were small I put some stones in the tank so they could find some cover. Maybe one of these stones fel on the bottom with no direct results, but later when something happened(I have no clue what) during the night the bottom failed at this point. When the rays were getting larger and eat well I removed the stones(the tank has had only sand in it the past year)
I still have some pups of these rays indeed, and I am thinking of keeping them. It will take at least another 3 years before I would have rays like the ones on the photo again though. The 3 largest scobina females measured around 35cm (14") across which means they were fully grown.
The Hystrix were averaging at 30cm(12") across.
Of all the small rays I had , I only have my retic and a 1:1 group of Hystrix. One the female that gave birth the other day I put here in a seperate tank. And 2 days before the crash I seperated a male as well becuase his disc was damaged.
The worst of all this, is that in about a months time my new fishroom would have been complete and all these rays would have been moved to new larger tanks.
Monday the insurance man is coming to inspect the damage, I hope thhat this turns out well.