This is growing inside one of the galvanized stock troughs. It's new to me. The others have green algae, but this one only has this white. It is making the water opaque, sort of like if you poured milk into the water. There are goldfish there - or were the last time I got a glimpse of them. The water is too cloudy to see into. I'm in the process of using up the water here so I can clean the trough and start over and when dry it's texture is like chalky powder. I'd think it was mineral buildup, but this is primarily rain water in this trough.

Edited to add that I see no green in this at all. Without any sign of photosynthesis, I'm thinking it may not even be a plant, but something else. The same water is growing green algae in a rubber trough next to this one. No white growth in it.

Maybe Tin pest
https://en.wikipedia.org/wiki/...
https://youtu.be/sXB83Heh3_c

galvanized sheet metal is bright silver grey, creates a similar artwork as frost on the window

Possibly what is called white rust? A form of oxidation on galvanized metal exposed to rain/dew etc.

http://www.unionmetal.com/pdf/...

Thanks. I think I'm gonna go with white rust. This is the newest (this year) of the galvanized troughs I'm using and the worst accumulation is the upper 1/3 of the inside of the trough. It formed under water, but where the sun would have been the strongest. I'll bet when I get it empty and cleaned I'll be seeing more normal rust spots where the zinc has gone and exposed steel.

You are most welcome. I remembered something from a conversation with a chemist friend about galvanized buckets...one of those bits of trivia floating around in my head.

I'm wondering if you should link this thread to the farming forum to ask for ways to correct/prevent this and extend the life of the stock tank.

well the question now is if this is safe for the fish in there? You said it formed where the sun was the strongest, moving it to a shaded area should help prevent it then I would think. Plus goldfish will not live in a metal tank if the sun is on it, the water will heat up way too hot for them and they will die. Goldfish like cooler water. Do you have anything moving the water around, an aerator-something to add oxygen, like a fountain or bubbles?

Actually I have goldfish in the galvanized tank at the barn. It is in full sun, all day, in Texas. Yes the water gets warm, but the fish do fine. I think in these large tanks that are meant to provide livestock water the temperature doesn't get as hot as you'd think and I think feeder goldfish aren't very delicate about their living conditions. At least that's been my experience. If the water is allowed to get low, then raccoons and possibly some birds may extract them. No aerator. I used to worry about it, but they do fine without it. Eventually they get pretty large. Sometimes they commit suicide by jumping out. I have to watch when I'm deliberately letting it overflow to skim trash and algae off the top. Another metal trough is primarily in the shade. Both those are growing green algae, but this one is in shade about 1/2 day. It's the newest. If I can catch any fish in there, I'll relocate them or put them in a rubber trough until I get this one coated. It has to be in this location to catch runoff from the roof, so moving it isn't an option. The fish are there to help with mosquito control and they do a lot better job of doing that they are credited with.

We keep goldfish in our tanks too - some in full sun. The only problem with them getting too hot is if the water level gets very low. For that reason I have "river fish" in some of the smaller troughs. They also control mosquitoes but tolerate very warm water. I don't know what they are, but I catch them out of the pools left behind when the water in the river gets low.