Can anyone ID this thing?

OK, so I ended up getting 2 different types of flatworms in my Marine Planted tank, one is the standard greenish flatworm and the other is a tan type of thing that doesn't have the same shape as the green flatworm.



I got some of the salifert Flatwom exit and it decimated the green flatworms in about 5 minutes. And seemed to agitate the brownish ones too (as well as my dwarf ceriths, but they recovered). The brown things fell off the glass, some floated away, other bigger ones didn't move.

Now fast forward a week: the brown ones seem to have repopulated already and are all over the glass again. Are these true blue flatworms or some other type of nuisance simple organism? I re-treated my tank today with around 250% of the suggested dose of Flatworm Exit, and the same results as last week: stunned ceriths and disoriented brown things, the bigger ones unaffected.

If they are a flatworm, any idea why flatworm exit didn't work? HAVE I SOMEHOW BRED SUPER FLATWORMS?

I've attached a drawing since I don't have anything besides a phone camera and these guys are slightly too small to capture.

Thanks for any help you can give with this, it's frustrating.

 

They are indeed flatworms.

Some flatworms are photosynthetic as well and limiting the lighting period or doing a couple day black out will help. If you are feedig this tank that will increase their numbers as well.

Some damsels love to eat these things and are more likely to do so if the tank is not feed for a couple of days forcing them to look else where for their food.

Boy I feel for you, I would not want to fight the flatworm battle again.

Best method other than flatworm exit I have found is dipping corals and rock work, and using a flash light at night beamed on the tank for an hour or so to attract them and then syphon them off.

How long did you leave the medication in the tank, without pumps on, or chemical filtration before you started the water changes. ?

 

Probably about an hour. Today I left it in 6 hours before I added carbon to the system. No water change this time since there weren't nearly as many of them as the first wave; I'm not concerned about the toxins. I'll have to try the blackout + flashlight tip the next water change I do. Thanks for the tip.