I never could get blyxa to grow in my flourite tank (peristaltic EI dosing, pressurized CO2, pH controller, 4x55W CF 75 gallon) - a medium light, high tech tank.
It great perfectly well in my cheap potting soil + red clay capped with pool filter sand 20g tank. It did have 1x55W (old) CF light and DIY CO2, but wasn't a very spiffy tank overall.
I assumed it was the roots didn't like the flourite. Now where'd I put those empty tanks!
That's the perfect excuse to get multiple tanks!