[squidsquiggle]

According to Hoppy's amazing chart, one T5 HO on my 21" tall tank should give me medium light. Is there any significant change to this if the light has no real reflector (just white paint), and the tank has floating plants? The light would be right on top of the tank.

 

[Hoppy]

Those charts are for T5HO lights with very good reflectors. The reflector can increase the PAR from the light by a factor of close to 3X. So, with no reflector you could get as little as one third of what is shown on the chart. And, with poor reflectors, you would get something between that and what the charts show. Floating plants cast shade, so of course they reduce the light intensity below them.

 

[squidsquiggle]

Those charts are for T5HO lights with very good reflectors. The reflector can increase the PAR from the light by a factor of close to 3X. So, with no reflector you could get as little as one third of what is shown on the chart. And, with poor reflectors, you would get something between that and what the charts show. Floating plants cast shade, so of course they reduce the light intensity below them.

Thank you so much, Hoppy. Exactly what I needed to know.