needs 1000 gallon for fully grown, 300 will only work for survival, but it wont be thriving in 300 gallons, similar to bamboo sharks, 180 for survival, 600 for thriving. Theres a humongous difference between survive and thrive. I think thrive should be the minimum for long term housing, survive is the minimum for quarantine or short term housing (no more than a month), that is how it should work
Either way 75 gallons will only work for a couple of weeks before its too small for it, i urge you to reconsider fish choice unless you have a larger tank. If you have a 1000 gallon tank great, i hope you like this fish