Algae on Glass not on glass??? how?


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Jul 17, 2019
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I have a 125 gal reef and wipe brownish algae away on the inside of the glass for as long as I can remember. I have been performing weekly water changes of 20% for years. Went on vacation over a week ago, had someone come to the house and wiped the glass. I haven't done a water change so coming on two weeks now. The 'big' change is the glass has NO algae build up and that has been now for two days. I have not had to do any wipes, could the skipped water change be the cause? no other changes has been made, I am thinking to hold off the water change to see but then afraid to do and have algae come back. Thoughts?


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Oct 29, 2023
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North Andover
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Water changes add in all sorts of trace elements and the like that do help algae but also coral grow. It is very possible that reducing water changes may help with reef stability and a reduction in nuisance algae if your nutrients are balanced and everything else looks good. Have you tested phosphates and nitrates recently? That may be important since it is possible that low nutrients also affect algae growth.


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Feb 19, 2023
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Council Bluffs
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Monitoring and Testing become very important when you stop doing water changes. I monitor Salinity, Temp and PH, and I test every other day, every 3 days for Phos, Nitrate, Calc and DKh.

My tank is almost 14 months old and i haven't changed water in 6 months now. I stopped doing WC due to a Cyano outbreak, and elevated phos levels, once I got the phos under control, my ugly algae went away.

My tank uses a little Calc, so I have to dose about 40ml of Reef Complete weekly.
DKh fluctuates so I dose Arm and Hammer baking soda mixed with RODI for that.
I have elevated PHOS. Pretty sure it is leaching out of my rock still, so I am dosing 38ml of LaCL/RODI mixture everyday directly into my skimmer. I use Seaklear commercial Lanthanum Trichloride (9000ppm in 10,000g water) 20ml diluted with 1480ml RODI water.

Monitoring and Testing become vital too maintaining water stability when you stop doing water changes, I'm glad I went this route now, but at first it was dicey getting used to the testing and getting into a routine.

Since I'm around 6 months into this no water change, so I am getting ready to send a sample out for Trace element testing to see what, if anything I need to add, but I am pretty sure the Reef Complete I am using is putting trace elements back into my system.

Like you I went from cleaning glass every day, to cleaning it about 2x a week I think.

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