I have a problem similar to loverofkoi, regarding small creatures in my tank. I know these are not worms but they still concern me. Whatever these creatures are, they are smaller than a flee and have a white to almost clear color to them. They are only in my tank at times and they get washed away when I clean my tank. They just keep coming back. The first time I noticed them, I thought they were tiny air bubbles. After watching them I discovered that they would swim down to the rocks and crawl around. My concern is that they are some kind of parasite, and I do not want them to harm my fish (one female betta, and two other kinds of fish). Can someone please possibly let me know what these tiny creatures are and how I might be able to get rid of them.

P. S. They are about the size of the periods on this page.

Can you describe them more? They are whitish clear and very small. How do they move (jerking, straight)? Are they always free-swimming or do they walk or crawl? Do they leave the water? I have aphids on the surface of my tanks but they can't swim under the water. If they are jerk swimming around, they may be some sort of copepods (many kinds of various sizes) or daphnia (although they usually get larger). They could even be babies of certain larger animals like scuds (like shrimp) or aquatic pill bugs. My tanks have a few copepods and planaria that I find in the waste water after changes. It's normal and healthy. If there are a ton, it's usually due to overfeeding.

As for them being parasites, it's very unlikely. Most parasites must live on or in the host and cannot live alone for very long. If these things were parasites, they would be attached to or inside your fish and not swimming around. In fact, the fish may even eat some of these small animals which I suspect are harmless.

If they are really as small as a period, then you could put some under a microscope to see what they look like up close for better identification and description. There are hundreds of tiny animals that find their way into freshwater systems so there are many possibilities.

Yes they are clear. They just kind of float all over the tank most of them swim to the bottom to crawl on the rocks. I know there are over a hundred of them in my tank probably a lot more. I don't think that they are quite big enough for my fish to eat them, to the fish they probably look like air bubbles. They only appear in my tank after about a month and a half after I clean the tank. I clean the tank about every two months since it is not that messy due to the fact that I only have three fish in a ten gallon tank. Anyway thanks for the help I am not as worried now, maybe I will have a better description of them when they come back.

Wow! You clean your 10 gallon tank every 2 months! Even in my tanks with few fish, I do weekly 50% water changes with gravel vacuumings. Smaller tanks get worse faster. Even though you have few fish, by letting things go so long, that's why the copepods or whatever they are have a nice field day! Clean the tank more often, and they won't be able to accumulate to such high numbers.