What is this?

I have a 20 gallon newly set up tank. It has some live sand (and other gravel, crushed coral, sand and rocks), some plants, and some nerite snails. I haven't added fish yet. The water is a little white which I figure is from bacteria. Lately there have been developing on the glass white circular patches. I call them circular, but often they look a little more like Pacman shape because there is a sort of wedge shape area that is less white looking. There are two in this picture. On above the big gray rock and on at the right end of the rock. I scraped some of the glass yesterday and found more this morning. Not sure what they are.

need a clear picture of whatever you mean.

what sort of fish do you plan on keeping?
why have crushed coral and different sand together?

Zoothamnium ! They're common in new setups, they feed on bacteria in the water. It's a living microorganism.

Not my video, but a close up of them

They will reduce in number as your tank matures over the following year


They're mostly harmless and normal in many tanks, bur large numbers like yours is normal as a new tank starts out and works to find balance.

Colin_T said:

need a clear picture of whatever you mean.

what sort of fish do you plan on keeping?
why have crushed coral and different sand together?

Click to expand...

I need the crushed coral because the water is acid and soft and I want livebearers. I don't want white substrate, I want black. I need to test the water again soon and see if I have made enough difference, maybe need to put it in the filter. Anyway, there are reasons for each choice I made, some aesthetic and some functional.

CassCats said:

Zoothamnium ! They're common in new setups, they feed on bacteria in the water. It's a living microorganism.

Not my video, but a close up of them

They will reduce in number as your tank matures over the following year


They're mostly harmless and normal in many tanks, bur large numbers like yours is normal as a new tank starts out and works to find balance.

Click to expand...

Thanks. That doesn't look like them. This is solid flat on the glass, not floating around. My aquarium back looks polka dotted with patches of them growing flat on the glass in circles.

I'll try to get better pictures, but I'm having difficulty focusing on it.

Trying Again said:

Thanks. That doesn't look like them. This is solid flat on the glass, not floating around. My aquarium back looks polka dotted with patches of them growing flat on the glass in circles.

Click to expand...

They don't float around all the time. They also could be vorticella colonies, a similar microorganism, or even stentor. Same deal with them too. Most of the time people notice them on glass, plants, or hardscape.

I'll look at the video again -- I was in a hurry this morning. Here is a better picture from the wall of my tank. I put something solid black behind them. I probably have about 10 more round clusters on the glass on the back of my aquarium. Each of the clusters is smaller than a penny and bigger than a pencil eraser.

I don't see any stems on mine. They don't look like little trees or little dandelions, just clusters of specks stuck on the glass. I searched for more pictures of the species you showed and there is some variety, but I didn't see anything that looked like this -- maybe I just didn't find the right picture, but I've been searching for a match for a couple of days.