TMC LED light query

[Will Ingram]

Hi All,
I have a 50L fishtank with some small tetras & 3 'Dwarf Curviceps' . It has a few plants- some Cryptocoryne (doing well)
and some background hornwort rotted in some laterite, doing well.

Anyway, the tank is lit by a TMC 'Grobeam' 500 LED light on the scale up/ scale down TMC controller. It is at 60% of maximum for 4 hours in the middle of the day, and takes 4 hours to warm up and scale down to off (as it would in the great outdoors), this is the great feature of the controller.

Anyway, compared to my old 25W T8 tube, it is -bright-, especially as the tank is only 12 inches deep. The fish are, to be honest, a little be afraid of it and the dwarf curviceps only come out morning and evening.

My question is, to keep the plants growing would it be better to keep it at 60% maximum power but for a much shorter period (e.g. 11am-2pm) or should I keep the same time schedule but reduce the power to 30-40%?

I am not bothered if the plants grow slowly, just that they don't wither or get smothered by algae. Trying to get the best colours out of the fish is my aim here.

Any comments welcome.

Cheers
Will

 

[sanj]

My inclination is not to reduce the power, you could reduce the max output time, i guess. The only thing is that grobeams produce less PAR than the marine versions since plants do not require as much, but given that you are talking 60% max of a growbeam perhaps you dont want to reduce it much more.

Just looking at the PFK article on par comparisons, depends on how hight you are mounting your unit above the water, but at 8" they used averaging around 150 at 30cm and you only need around 30-50 perhaps.

just say Growbeam = 80% of the marine HD1000 (i dont know how much weaker it is) so thats 120 and then *60% = 72.
Yet that is for 4 hours. If you did it for 2 hours you would still have enough PAR for the plants, you probably want to aim for at least 6 hours over 30 PAR to be safe. Low light plants possibly can grow in less but unless you know i would not push it too much.

The answer would be to experiment with levels little by little and watch how your plants react.