Yup, that's BBA alright. Always a fun thing to battle :sarcasm:
I took out the filter outtake and return hose and have them soaking in h2o2. Almost immediately the algae turned a clear color and is deteriorating. I really hope it doesn't spread in my tank. My last resort would be the one two punch method but this is occurring in my RCS tank and many have reported heavy shrimp casualties with the method so I'm definitely going to be cautious.Sadly it is BBA like the others have said, a good thread to check out in the "One-Two Punch", I am testing it out now in one of my aquariums, so far the first treatment has cleared up the BBA but the BGA seems unaffected. You best bet would be to try and manually remove as much as possible, disconnect your filter and clean it with and H2o2, this will help clean out your filter tubes from BBA. The biggest success I have had keeping BBA in check are TSAE.
There's no light in the filter so there's no BBA.You could build a shrimp trap and store them in a bowl of water for an hour while you treat your tank. If it is on your intake and out flow hoses more than likely it is also inside your filter, so you will want to clean this with H2o2 as well.
The tubes are a clear green, best bet is spores have gotten down the tubing and into the filter. You can believe as you wish but when I had BBA I tried the blackout method and BBA does just fine in near darkness, you would be surprised how little light it needs. But do as you wish. Might take you ten minutes to clean it, not that big of an investment, if you ask pretty much anyone on this forum if they could spend ten minutes to help prevent the spread of BBA in their tank if they would do it, and I bet the majority of them would.There's no light in the filter so there's no BBA.