How to achieve clean macroalgaes

[KilianSP]

Since i got alot of different types of macroalgaes and one frag tank is currently on hyposalinity, i wanted to prepare the replanting of the frag tank.
How do i assure the macroalgaes i put in there are aptasia and sea lettuce free?
I am struggling with the sea lettuce right now, since it is going to overgrow other macroalgaes, and it even appears in thanks where i thought i put clean macroalges in (no obvious signs of sea lettuce and aptasia on the frag)
So what should i do?
The frag tank should be clean after 35 days of hyposalinity or not? Atleast i hope i killed every sea lettuce and aptasia cell by doing hypo.

I would start by making small frags, clean them under magnification, and then wash them in fresh saltwater. If i can't see any ulva or aptasia under a scope, there shouldn't be any, am i right? And Washington them in fresh saltwater should remove smaller bits?
And then i am Petting them in an old freshwater tank with new saltwater in it for quarantine, but for how long till i can say it is Pest free?

 

[KrisReef]

I don’t know but I would put elevated nutrients into the qt to see if any hitchhikers start growing in there.

 

[KilianSP]

I don’t know but I would put elevated nutrients into the qt to see if any hitchhikers start growing in there.

For how long would you do that?
Whats the time when i know there is nothing on there, a week or even more?

 

[Dan_P]

I don’t know but I would put elevated nutrients into the qt to see if any hitchhikers start growing in there.

Clever!

 

[AydenLincoln]

I personally dip them in freshwater/run them under running water and visually inspect them. Regardless of what you do nothing is ever foolproof.

 

[KrisReef]

For how long would you do that?
Whats the time when i know there is nothing on there, a week or even more?

I put a frag of zoa's growing on a small piece of liverock into a tank once, and about a year later I noticed caulerpa growing from this tiny piece of liverock. I pulled it out, cleaned it off and put it back in the tank. A year later caulerpa sprouted again! I believe I threw the rock into the trash at that point. I don't know how long is a proper interval for confidence but as someone else mentioned these hobby methods are not foolproof. Sorry,