Bubbles

[Spillars14]

Can anybody tell me what's going on with this fish

 

[fluttermoth]

Your fish (a mollie?) has 'ich' or whitespot.
 
You will need to treat it, either by adding salt to the water (mollies are fine with salt, but some fish aren't, so check before you add any) or with a medication from your local fish shop (LFS), or by raising the temperature (but it does have to be quite hot, and again, some fish won't cope with extra heat).

 

[sawickib]

Yep fluttermouth got it, definitely ich.

 

[fishman2014]

welcome to the forum

 

[Meeresstille]

Is it laying at the bottom of the tank? 
 
Not having much experience with a fish that sick, but I'd first try to get more oxygen into the water. This is easily done if you have a Hang Over The Back (HOB) filter, a waterfall type filter, where you lower the water level in the tank to create a bigger splash as the return water falls back into the tank. You can also get an airstone (you need a pump and some tubing along with it)!
 
Compare some other pictures of fish with ich and research heat salt treatment for ich. Introduce the treatment slowly to allow your fish time to adjust to the changes in the water (salinity and temperature), at any signs of distress lower the treatment.
In a bare bottom tank such as yours it will be easy to pick up any of the fallen ich cysts by doing daily gravel vacs, ensuring less chances of re-infection.