One way to tell is to smell it. It smells atypical of any aqua plant/alage to me. Also, check out
this thread to see if you have Clado (contains Clado close up pics on first page and pics of Clado clumps on second page):
I battled it for 3/4 year, but finally got rid of it. In the end, after many lost battles, it was a multi-pronged attack which worked for me:
- Pull any large clumps you can (lucky that it's somewhat easy to remove)
- Yank any bushy plants which allow clumps of it to form (for me, that meant chopping up a huge, lovely 1' clump of blyxa japonica and planting it more sparsely where the Clado couldn't form a mothership clump
- Weaken any bits that remain: 5 day total black-out (completely wrapped tank with black plastic with only an aeration hose feeding O2 to the tank)
- Perform frequent water changes (I did 50% changes every 5 days for weeks until it was gone). Clado seemed to dwindle with great (not just good) water quality for me (others say this doesn't affect Clado)
- Spend 10-15mins a day looking for any sprigs in your tank - Pull any bit you see! Seriously, if you're walking by your tank, and see a bit on the substrate or floating around, stop what you're doing and pull it from the tank! I had a long pair of tweezers next to the tank for about 6 weeks for this very purpose.
I also had success spot-treating a patch which was embedded in my HC carpet with Excel. I used about 40ml via a syringe on a 2-3" patch of HC which had some Clado growing through out it. While it killed the Clado, it also took some color out of the nearby HC, but that recovered after a couple weeks.
Good luck!!!
Will