Any chance of a picture and short 20 second video of the fish?
If the pictures are too big for the website, set the camera's resolution to its lowest setting and take some more. The lower resolution will make the images smaller and they should fit on this website. Check the pictures on your pc and find a couple that are clear and show the problem, and post them here. Make sure you turn the camera's resolution back up after you have taken the pics otherwise all your pictures will be small.
If the video is too big for this website, post it on YouTube and copy & paste the link here. We can view it at YouTube. If you are using a mobile phone to take the video, have the phone horizontal so the video takes up the entire screen. If you have the phone vertical, you get video in the middle and black on either side.
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How long has the tank been set up for?
How often do you do water changes and how much water do you change?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the tank?
How often do you clean the filter?
How do you clean the filter?
How long have you had the fish for?
Have you added anything to the tank in the last couple of weeks?
How long has the fish been fat for?
Did it get fat overnight, or over the course of a couple of weeks?
Is the fish still eating normally?
Is the fish pooping normally?
What's in the imagitarium medication?
Do you have carbon (black granules) in the filter?