@betdempster
Let me see if I can address some of this from my own experience.
As for h2o2. It’s pretty benign stuff. All it really does is bring down the pH to a level where things like algae aren’t as likely to form. The regular 3% stuff added to water doesn’t really pose a risk to anything.
While I do support the idea of adding some nutrients to potting mix when rooting cuttings… I typically wouldn’t advise it when rooting in water. That will increase the likelihood of algae forming as you are feeding it.
The other thing about rooting in water is that I would tend to keep it in lower light… Especially earlier on when there’s no green grow since it’s not necessary then anyways. Increased light will promote the algae growth.
Changing the water very frequently will also assist with reducing any algae growth. I would consider changing it even daily. In the case of my hydroponic system where I can’t change the water frequently… I added a small aquarium style air pump with a stone aerator. This solved all of my algae problems and keeps the water from becoming stagnant… But frequent changing I think is your best bet.
If you do change the water daily… I think you probably could add a small amount of soluble nutrients without giving algae time to grow
One more consideration on rooting in water. What is your water source? Different people will have different opinions on this but…. My thoughts on using good, clean distilled, spring or even well water… While generally great stuff… Will also allow algae to grow. Something like your typical, treated municipal water will have chlorine or chloramine or something that inhibits algae growth. While in many parts of our lives, we don’t want this… In the case of rooting cuttings, it will actually be less prone to growing other stuff you don’t want. Like algae
If you think you can pot them up without damaging the roots… And I don’t think that’s a bad idea
If you’re getting algae in your fig pop bags… I think excessive light is probably the issue. I would keep the pop part of your cutting covered in foil or otherwise somehow in the dark.
I hope this helps