Planted Tank Enthusiast
Join Date: May 2003
Location: Blackwood South Australia
Remember that the WPG rule is only a guide, however 170 watts over 55 gallons is three watts per gallon, you should get great growth and be able to grow anything you want. At this level thought you will need CO2, either pressurised or DIY.
If you feel that three watts is not enough you could get two units.
Anyway why not see how it goes and buy with a view to adding another unit later?
Eheim Pimp Club member #3: Scribe to the Eheim Pimp Club
90 gallon, CO2 dupla injection, Dupla substrate heating, Dupla Laterite with iron stone substrate, Aquastarlight future 3 x 150 metal Halides, Eheim 2026 pro2's and heavily planted with Discus