strange things in one of my tanks

[duendecillo]

In one of my tanks, a 15g with a male betta in it, I just found some weird things.
The water has been very cloudy for a while, and I was told that this was because of bacterial bloom, or something like that, and that it would dissapear with water changes.

Now I found on my heater a white, hard, nest-like thing. I looks like white lavarock that has grown on it. I had to use a knife to scrape it off!

I started inspecting the tank closely now, and I found lots of little moving dots between the gravel.

So, my question: what are these things

 

[Aqua_Princess64]

Umm... I'm not really sure what it is, but I had something like that happen to one of my tanks a while ago. I decided to do some water changes. The fish died. I changed the whole tank along with the filter cartridge. The fish still died. I ended up having to completely start my tank again with new gravel, filter cartridge, etc. It was not fun. But after that, I never had a problem with that tank again.

 

[luxum]

Do you have an apple snail in there? The "nest" sounds a lot like the the way they lay their eggs, and all the little dots in the substrate could be baby snails.

 

[duendecillo]

no, there are only small snails in it, but they couldn't have anything to do with it I think.
The white nestlike structure was really hard.

and the little brown dots floating around: I've checked them under a microscope, and they are oval creatures with transparent legs and hairs... really creepy

 

[duendecillo]

I've tried doing some research, and it appears to me that the small things are some kind of ostracod (or mussel shrimp), but I can't seem to find what they do to an aquarium...
any ideas?

 

[jams.alaskan]

The hard deposit is probably calcium or another mineral that built up. They often appear on heaters and along the top edge of the tank. The small creatures may not be harmful but I'm wondering what they are eating - do you have leftover food in the tank? My fish would probably have them all eaten before I could see any...

ALASKA

 

[duendecillo]

there's only a betta in there, so he can't eat them all, and they are in between the gravel... so he can't even reach it.

about the calcium idea, it could be, but I doubt it, cause underneath the white layer, it was brown...