Algae in saltwater mix container

[gray808]

I have an RO/DI, and use a 28 gallon rectangular Brute container with lid to mix saltwater. It's white, because that is the only color I could find. It always has the lid on it, and it rolls away under a counter in the room that it is in. The room gets dim, diffused light, when the lights aren't turned on (it's a bathroom and we have kids, so sometimes it gets left on). Since it's rolled away, really only one side of the container is exposed.

I'll mix up 25 gallons or so of saltwater, then I use it for water changes, usually in about 8-10 gallon segments. The water is kept still and at room temp (~70-75F).

After a few weeks I start noticing an odor from the container, kinda musty, and will get little brown patches on the sides.

It may be complete coincidence but last week I did a water change, noticing the musty smell, and this week I've had my first outbreak of what I think is cyano (purple-red mats on the sand and some rock, green on the glass).

1) could the be related? Just in case, I pitched the last 10g or so, scrubbed the container with a couple capfuls of bleach, rinsed well, and am making new SW.

2) How can I prevent the algae growth in the container?

3) Would taping some thick black trashbags around the container help?

--Gray

 

[ShepherdReefer]

Hello Gary, I clean all my containers with citric acid and RO water. I first add the RO water and add some citric acid mixing together with a powerhead for about 20-mins. During that time, I will wipe the side down a few times. Then I will drain and rinse with new RO water a few times, and dry...all done.

 

[gray808]

I'd really rather not have to burn 20+ gallons of RO water every couple weeks.
I am looking for preventative measures.

--Gray