Mechanical filtration such as ?Does not sound like cyano if ChemiClean did not kill it. I would be hesitant to try anything.
You can't get rid of cyano it is ubiquitous. You have to change the balance so it does not create mats that look bad.
I struggled with cyano for a long time. I installed a UV without success. I used ChemoClean which turned into a slow running disaster in my case. In the end the cyano came back. I tried MicroBacterClean and it worked for a few weeks.
I saw a video by @Coral Euphoria and Abe simply removed mechanical filtration. I removed mechanical filtration. The cyano is now in check.
I think it can 100% be eradicated but you have to solve the problem causing it as mentioned above