If it is for long-term storage (more than a couple of weeks), you will need to add some unscented chlorine bleach. I have never done a calculation for 2500 gallons, but I believe it is 1/4 cup for 5 gallons. i have an earlier post with a link to a podcast on this issue, and with a chart in the post.
Here is the link to the old post. My post is post #4.
I couldn't find one that did better than the Pro Pur, and you get a discount by going through infowars to get it.
I have a 1500 liter water tank (white) and we never have had a problem with algae growing in it. We also rotate the water in and out of it (which is what you should be doing anyway to a certain degree) and both of our tanks are out in the desert area.
I agree and yes I would worry about the chemicals as well. But maybe the filter would take care of most of them
Old Man I don't use any filtering system on the water tank. I do filter my drinking water with a Berkey Water Purification filters. You can make one using Berkey filters as well using food grade buckets. I'll post a follow-up link on this as it will be helpful for other people here. Again I am speaking from personal experience. I live in the desert both in West Texas and Egypt and we add nothing to our water tanks that are white in color. Actually IMHO black will attract heat which will cause algae to build up. Think about it, when you make a solar oven system you paint the inner part of the system black to attract heat, white is used to reflect heat. Being in the desert we don't have a issue in terms of heating things obviously so white is the color of choice. Again anyone who has a solar hot water tank paints the tank black. So from a practical point of view I would stay away from black tanks as they may be the cause of algae build up due to the black color attracting the heat. Just a thought.
