White Water Tissue Mold - Hazards, curing, etc


LifeTime Supporter
Mar 12, 2008
Hatfield, PA
Hello all,

Thought I'd post a new topic on a new but seemingly rare problem. I pulled my light niche today to replace the bulb (incidentally all it needed was a bulb - yay) and LOTS of flaky brown/white tissue like stuff came out of the niche. It seemed like an absolute ton! It coated both the niche and the housing. When pulled from the pool it was white and slimy. Very nasty. I assume white tissue mold. My assumption is that when the light is powered up, it causes water circulation which would allow the hot water to escape from the top holes and draw cold water in through the bottom holes. The woman that lived here had some financial issues and the light bulb was burned out - perhaps for years - so this cycling of water never happened. That's how I assume the mold grew.

My numbers:
FC 0
CC 3-5 (though MPS is affecting it)
PH 7.4
TA 130
CH 350
CYA 60
Temp 70

As you guys have read in other threads, my crystal clear algae and ammonia free pool still refuses to hold an FC level despite a very high CC level on DPD and FAS-DPD tests (registers 0 on OTO test). I've been simply operating on a maintenance dose of chlorine that mirrors what others do - 2 qt 6% per day for my ~~ 20,000 gallon pool. My treatment for this mold was to clean it as best I could by vacuuming up all the pieces, and cleaning the niche the best I can. Then I dosed it with 2.5gal of 12.5% as well as 4 pounds of MPS. That *should* be one heck of a shock. I was wondering if anyone could comment on how dangerous this stuff is if it becomes a problem. Despite how cold the water was today, it was nice to swim in it once I got fully immersed.


The housing is coated in the slime - as is the cord and everything else not seeing light.

The niche is actually light colored - this is before cleaning

Better pic of the mold.



TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Problems in a light niche are fairly common, what is rare is people actually looking in the light niche to become aware of the problem. The circulation is poor in the niche even at the best of times. Once something gets going in there it is difficult to kill off without removing the light.

The mold isn't any more dangerous than any other clump of slimy muck. That is, it might be a little dangerous but normal day to day precautions will take care of it, ie kitchen gloves and washing up afterwards. Once the niche is open to the pool some vacuuming up of any debris that comes out and a little brushing inside to expose everything to the chlorine in the pool water should kill everything.