i don't think stop fertilizing and lighting is a good thing to do.
one should concern that,
the main reason which introducing algae in our aquarium is high PO4 and NO3 level, especially PO4.
this happen when the tank is under an unbalance situation,
i.e. the glowth of plant is limited by some factors, for example, light, CO2, trace element...etc.
for your tank is using HQI, i assume that there is more than enough light and CO2,
so the limit factor is trace element.
plant consume NO3 and PO4 ONLY when there is enough trace element, otherwise the proccess will stop at a point where all trace element is used up.
so what you have to do is, let PO4 to be the limit factor of plant glowth.
you can do this by
ADDING MORE trace element (fertilizer). Generally speaking, 0.1 ppm of Fe indicate that other trace element will be fine too.
be sure to keep an eye on the Fe level, once you get the ideal level you have to reduce the dosage, otherwise you'll get another problem.
Stop adding fertilizer can't help to this situation, as PO4 and NO3 is produced by fish and food.
so, FORGET about stop fertilizing, stop lighting...etc. It may work sometime, but it will kill your plant together with algae in most cases. In another word, it's the last method you should concern.
remember what i've said in another post?
"One theory doesn't suit to all."
hope it can help u
