My original male was that big, then whatever hit them took the pair along with the rest in several tanks. For some unknown reason 4 survived whatever killed a couple hundred, and those 4 were kept in an unheated 30 long for well over a year. Put the pair int a 33 long with a heater long enough to spawn and the fry become free-swimming, then unplugged the heater.
The 4 survivors were among the small ones of the brood I had grown out, remains to be seen how big they'll grow or what their offspring will do. There was one really big male from that brood, and the rest were the typical range of sizes in a SA or CA brood grown out. Only thing I can figure was that the temp was too warm for them for too long, and it triggered something like an immune system collapse.
Whatever killed the oblongums didn't affect several pairs of cutteri that were sharing a tank with some, or even the tiny cutteri fry. I did lose a handful of BN pleco's along with the oblongums in the several tanks, but not all of those died either.