I have been battling clado in almost all my planted tanks for awhile. This stuff is relentless and almost nothing kills it.
I have had some luck with double dosing excel everyday in my 29g. It has definitely slowed the growth. I also hand pick out whatever I see and it doesn't grow back as fast as it was. I have also slowed down on my fert dosing (just forget sometimes) and it could be coincidence, but it seems to help as well.
I have tried double dosing excel in my 5.5g planted, but am not faithful in dosing daily. The clado comes back just days after picking it out of the entire tank.
I've read that clado likes all the conditions plants do, so its so hard to get rid of.
I just hate looking at it everyday and especially when it's pearling!!
I hate looking at it too....and I hate the smell of it when I pull it out. Its terrible!
Good luck! And if you start to see some good results, let us know what you did!