Economical Water tank treatment other than bleach?

[Sail Away 3]

Originally Posted by skipmac

I go with the idea to add a filter. I use bleach and run all drinking water through an ultrafine filter. Not only does it remove chlorine taste but also bacteria, amoebas, viruses as small as 1-2 micron.

I use a Seagull which I think is grossly overpriced but a very nice bit of gear. Got mine cheap but unused from a marine surplus shop.

After a short career in water treatment I am now quite cautious about my water tanks.
Some information easily available on the internet can help with your treatment.
Filters properly sized can help with Cysts but Viruses require a disinfectant to neutralize the cell. Chlorine, peroxide, ozone are oxidizers and damage the cell wall causing the cell to die or not reproduce. UV is like a fatal sunburn to the critters but with cloudy water, tiny things floating in it, and the little tykes can hide in the shade.
RO can filter out a virus as the membrane is tight enough and cysts like Cryptosporidium are relatively huge at 7 to 10 Microns

Copied from the internet

Filtration Sizing

Oct 16, 2015 - Because Giardia cysts are resistant to normal disinfection, filtration is usually required. Cysts are large in comparison to bacteria and viruses (ranging from 7-10 microns in diameter); consequently, they are more easily removed by filtration
Viruses can reproduce only within living cells. They are 0.004 to 0.1 microns in size, which is about 100 times smaller than bacteria. Cysts: Capsules or protective sacs produced by many protozoans (as well as some bacteria and algae) as preparation for entering a resting or a specialized reproductive stage.
Virus: 50 to 500 Nanometers.(1,000,000th of a millimeter.) Cysts; 7 to 10 Microns (1,000th of a millimeter.)

I hope this helps...