Aponogeton madagascariensis help

[cmax916]

I got 2 of these lace plants. I read somewhere said that they like cold temp. water like ~70. Is that true? When I got them, they have huge and tall lace leaves. Some of them had die off but I saw a couple of new leaves shooting out from the bulb. Anyone with experience growing this plant, tips are welcome.

thanks,
-mAx