Amount of water changing to beat algae

I fyou change 20% of your water at one time, you will reduce any bad stuff like nitrates by 20% (as long as they are not present in the new water). If you take water out and replace it at the same time you will be removing some of your new water as you remove the old. Suppose for example that you remove one percent of the water and then replace it and do that 20 times. You will have reduced bad stuff by 1-.99 to the power of twenty which is about 18% assuming perfect mixing. Better to just suck out 20% of the water and then replace it, I have done 30% water changes in emergencies. If you match salinity, pH and temp, you should have no problems in most situations. If you have something really delicate and susceptible to any change, the story might be different but removing bad stuff and replacing needed elements is always helpful.

 

i agree with 90 berlin joe, double check your phosphates and look into your calcium as well...if the calcium levels rise at a safe pace, some more calcareous algae such as coralline may start competing with your algae problem....

 

That seem kind of weak water flow for a 55gl. Maybe I missed something though. I have 2 MJ 1200 in my 20 going all the time plus an Aquaclear 70 HOB.
I think everyone would agree that 2x1200 MJ alone going 24hr wouldn't be enough for a 55gl and that could be playing a big role in excess algae buildup.