water tank

[t1bone]

We have a 275 gallon water that we use to fill our RV when boon docking. I noticed when we emptied it, it had some green marks in the bottom inside of the tank. I assume it's some kind of algae. We do not drink the water, but do dishes, shower, and flush with it. Is this a big deal? Is there something that will clean it, if I can get to it? Should I worry about it?

[EA37TS]

Originally Posted by t1bone

We have a 275 gallon water that we use to fill our RV when boon docking. I noticed when we emptied it, it had some green marks in the bottom inside of the tank. I assume it's some kind of algae. We do not drink the water, but do dishes, shower, and flush with it. Is this a big deal? Is there something that will clean it, if I can get to it? Should I worry about it?

Chlorine bleach.

[lwmcguir]

Blue green algae which is cyanobacteria

As noted any halogen will kill it layer by layer as well as peroxide.

Use a dark tank, never use a translucent tank for water in the sunlight

[16ACE27]

Originally Posted by t1bone

We have a 275 gallon water that we use to fill our RV when boon docking. I noticed when we emptied it, it had some green marks in the bottom inside of the tank. I assume it's some kind of algae. We do not drink the water, but do dishes, shower, and flush with it. Is this a big deal? Is there something that will clean it, if I can get to it? Should I worry about it?

Short answer - No.

And I suggest you never look inside an open cistern.