That's the thing. I've had those too. They went away.Yall do realize that flatworms can release a toxin that will kill the tank.. I'm not the pros yall are but I have had way too much bad luck to chance it.. I have rust brown flatworms.
Weirder I didn't kill them. And my tank didn't die. I had a sponge die and killed a bunch of stuff. B
Folks I think sometimes overreact to the introduction of a new species in a tank. The actual advice from the real experts is to watch them in large populations. Sometimes esp in a really dirty tank if ya get flatworms the population explodes. I mean explodes. See you tube. Then they smother corals and die in poulations large enough to affect the tank. But Think about that what does that many look like holly Halloween nightmare. The 30 I can count I really don't think is gonna do any thing. And really used to think I had a dirty tank. Guess not.
I do have a lot of weird beneficial bugs though. That's a pretty hefty CUC. In my 30 I only have 2 snails I actually bought as a cuc. Rest is hitchhikers. I got the flatworms in there too. No explosion.
This brings up the use or over use of meds and poisons. What's worse the illness or "infestation" or the cure esp if you consider the long term health of the tank and inhabitants. I think of it like chemotherapy to your tank. Hit it with a narrow band toxin that targets one thing mostly but it does effect everything else. We know what chem looks like in people. So if it's not a healthy tank in the first place it maybe even worse.
I think it needs to be a case by case look and if ya have a few get something else's that eats it. Rather than the automatic reach or insecticides. The current eww a bug attitude in Reefing is probably something that needs to be taut differently. . It should be looked at as basic husbandry. Again.
Keep an eye on populations and cull when you need too. And if ya get something really bad cuz ya didn't qt. then nuke. It's safer better advice for a newer reefer than nuke first. There's safe ways. It's actually better advice for older reefers too.