Oily RO water?

[BLUElobster99]

So I topped off my tank with RO water that I made myself and put into a plastic jug. When I poured the water in it look like I was pouring in an oil substance. Is this normal when RO water is added to saltwater? I'm wondering if this is a chemical reaction or if my RO has been contaminated somehow. The tank is a cycling 20g with no fish.

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[Linwood]

From your description I do not quite understand whether you think it looked oily because it had a film on it, it made a film when added to the tank, or did it just show a distorted look in the water as you added it, which quickly went away?

The latter would be normal - pouring fresh water into salt, or salt into fresh, or anything with significantly different density or hardness will show ... I don't quite know the right term, but a distortion as it mixes. But it will go away quickly.

Oil will form a film -- on salt water or fresh. If your RO water is forming a film, it's bad -- something in the lines, in the container you used, the RO filter itself, something. A fish tank may form a scum film on its own that is NOT oil (e.g. bacteria) but if you pour water in and it immediately forms a colorful film on the top - you have a problem.

[BLUElobster99]

Yeah it was just the distortion. I was a little worried for a second. Thanks for the reply.

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[Mattyfelts]

since they are two different salinitys you can see the freshwater in the saltwater until they mix. look up under water freshwater rivers or lakes, basically a river of freshwater under saltwater.