Well that changes things, I'd suggest that it is possible that the less
light= less uptake so if you have a good size fish load, that might
cause it. Still, I'd think in most cases, I have several non CO2 tanks
as well(more than CO2 entriched), adding new bulbs often causes some
algae but not much.

I have so few algae issues in non CO2 tanks over long time frames as
rule also.

No water changes, lots of plants, good feeding and algae herbivores,
pruning mainly by topping, I do top of the tank once a week with some
KNO3/KH2PO4/Traces and sometimes GH.

SeaChem's equilibrium works nicely as it has most everything except N
and P.

You can also add the ferts once a week and then dose Excel also.

Excel often has a good effect on the plants and not so good for the
algae.

You will need more nutrients(KNO3/KH2PO4) and be able to do water
changes using the Excel.

There are two ways to approach it without addressing the light. I'd do
that first, then consider the new bulbs later.
Adding more light to an existing issue is typically a bad idea with
algae.


Regards,
Tom Barr

www.BarrReport.com