Fish Flashing?

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 use dechlorinated water for the water changes?
Do you gravel clean the substrate when doing water changes?

What fish are in the tank?
Did you add any fish about 3 months ago, just before this started?

----------------------
Ammonia, nitrite and nitrate will all irritate fish and can cause them to rub on objects but normally it is a protozoan infection. You can try doing a 75% water change and gravel clean the substrate each day for a week and that will reduce nitrates and help for minor health issues. However, it won't cure protozoan infections.

Do any of the fish have cream, white, grey or red patches on their body or fins?
Do any of them have small white spots on their body or fins?
Can you post a picture of the fish and maybe a short 20second video of them rubbing on things?

After you turn the tank lights out tonight, shine a torch on the fish and look for a gold sheen. If any of the fish have a gold sheen on their body, they have Velvet (Oodinium) and that can be treated with heat (30C for 2 weeks) or any white spot medication.

To work out the volume of water in the tank:
measure length x width x height in cm.
divide by 1000.
= volume in litres.
When you measure the height, measure from the top of the substrate to the top of the water level.

There is a calculator/ converter in the "How To Tips" at the top of this page that will let you convert litres to gallons if you need it.

Remove carbon from the filter before treating or it will absorb the medication and stop it working.

Wipe the inside of the glass down, do a 75% water change and complete gravel clean. And clean the filter before treating. Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Increase surface turbulence/ aeration when using medications because they reduce the dissolved oxygen in the water.

 

What type of fish do you have

 

Did you add any fish about 3 months ago, just before this started?

Do any of the fish have cream, white, grey or red patches on their body or fins?
Do any of them have small white spots on their body or fins?

Can you post a picture of the fish and maybe a short 20second video of them rubbing on things?

 

How long ago did you have whitespot (Ich) in the tank?

How long did you treat it for?

What did you use to treat it?

Can you post a picture of the fish?

Can you post a short 20second video of them rubbing on things?

 

The bumblebee catfish has a couple of small spots that could be colouration or something else.
1 spot is on the dark patch just under the dorsal fin, where it meets the body.
Several spots on the pectoral fin.

-------------------------
Assuming the water is good (0 ammonia, 0 nitrite, nitrates less than 20ppm, pH around 7.0), and there are no chemicals in the water that are causing the irritation, I would say there is a low grade protozoan infection in the tank. It could be whitespot, velvet, Trichodina, Costia, Chilodonella or something else.

You could try heat treatment where you increase the water temperature to 30C and keep it at 30C for 2 weeks. That should kill all the different types of protozoans in the water. Clean the tank and filter before raising the temperature, and increase aeration/ surface turbulence to maximise the oxygen levels in the water.

Or you could try medication again, but I would try heat first because it doesn't involve chemicals.