Well T5 HO light the
GPH rule is out the window... These things put out lumen ratings that'll blow your mind.
A little example and this is not totally accurate but a T5HO @ 40 watts would be the same as about 80 to 100 watts of T8 lighting or so... Speaking in terms of
lumens. So with that being said it would be possible that you would get some pretty intense algae growth with only a few plants to suck up that light..
If you really like the fixture you can get it just be careful with the light.. Do like a 6 to 8 hour light schedule and see what happens.. Then adjust from there if need be or you want to.