Actually the pump is a bad idea that I tried earlier- its too powerful. I just used syphon pressure. It sucks all the algae growing in the sand out and the Credit card scraper enabled me to remove any growing on the glass. I syphoned from the tank to the sump, collecting the debis in the attached stocking. you just have to watch the rate at which the sump fills and give the return pump a chance to catch up so it has to happen in stages.
Len, No, its not powerful for rock-attached algae, however, the bulk of my problem is (was 8) ) ) on the back glass and in the sand- probable cause is a deteriorating spectrum on one MH as its only on one side under that globe. There was some attached to the rocks- I pulled the relevant rocks out and scrubbed them with a brush. Whilst it is a symptom cure, I think I may have the cause nailed down now.