Yes, if the current fan is not enough, the next thing I will do is start changing the photo period. I did that last year but I tried not to do it as I want to look at the tank too!
I am kind of surprise that the tank is heating up so quickly. Comparing to previous years, I just don't feel that the weather is that hot yet. That's why I forgot to replace the broken fan I have last year.
Oh well, the worst has yet to come.