lighting for 80cm high tank

Try t5's instead, plenty of light for over 100cm.

Regards,
Tom Barr

would t5's penetrate to the bottom of the tank? its 80cm deep top to bottom so thats why i was thinking of going with the bigger halides

Each T5HO bulb will give you about 20 mms of PAR directly under the bulb. A pair of bulbs will give you about 40 mms of PAR. If the tank is more than about 30 cm front to back depth, just use two pairss of bulbs, with the two pairs widely separated.

thanks,

the reason i ask is im considering setting up a 180x100x80cm tank, and trying to figure out what would be the best lights to use