red algae

a new and troublesome problem has come to the pool. RED ALGAE!!!

My in ground gunite pool has defects in the old plaster like shallow craters. I have had black algae in these craters before but a little algaecide and shock with a vigorous scrubbing with a stainless wire brush quickly took care of it. the red stuff not so much.

It is also on the little plastic in the pool, ladder steps and skimmers. Water chemistry is good, plenty of chlorine, and algaecide, pH is 7.2 and total alkalinity is in line. On the plaster it is only in the "craters" where the surface is the roughest. The water is crystal clear and can see over 40 ft. underwater with a mask.

Anybody seen anything like it?

Post some current water testing results taken with a drops-based kit. Also tell us the volume of the pool and the type of filter you have.

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Originally Posted by hotshoe

Water chemistry is good, plenty of chlorine, and algaecide, pH is 7.2 and total alkalinity is in line.
Anybody seen anything like it?

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"red algae" is actually bacterial (cyanobacter) AND you would not have it if your 'water chemistry is good'. It occurs when the water chemistry is off. As Watermon said, please post a full set of test results.

I use test strips, and all parameters are in the middle of the spec. The water was NOT in spec when the red came to find a home. It took a bit to get here, but after getting the pH and total alkalinity in order, the rest fell right into place. just after a couple of days with the chemistry correct, it isn't taking care of itself. The pool is approx 44,000 gal. sand filter, and a power vacuum. I believe the pits/craters were caused by a pH imbalance way before my time. the smooth part of the plaster is just fine, but every crater is rough, and has a red deposit. If it is bacteria, a good should take care of it I would imagine. I am trying that tonite, pump off long enough to let the water stop circulating, and I'm going to pour the shock down the walls and hope it coats the sides with a concentrated solution.

Thank you all for your suggestions, and help.

Chris

test strips are NOT precise for water balancing. Get yourself a good test kit (recommended Taylor K-2006) to help prevent such things happening again and also to save you money on chemical additions! "Parameters in the middle of spec" are not a valid test results in terms of water balance. PPM readings with enough precision to be useful are. Strips do not have the precision (for example TA readings with a 40 ppm jump between color blocks are pretty much useless but are what strips give you. A drop based kit is 10 ppm which gives you valid information!)

IF you have pitting in a plaster pool then your water balance has been off (either pH too low, calcium way too low or TA way to low or a combination of the above.) Strips cannot test for calcium hardness at all, they test total hardness which does you no good. Therefore it is IMPOSSIBLE to achieve proper water balance for a plaster pool using strips.

A good test kit is a whole lot cheaper than replastering ( or even acid washing) a pool!