The gel crystals won't provide any support at all. It is what it says...jelly.
just imagine real jelly after one of the kids has stirred it up and messed about with it.
Use it quite a few times but got to the point where i didn't think it was worth the hassle. You have to wait ages for it to 'gel'. If you're doing a few vases, you've either got to make up a big bucketful and then dish it out....messy...or be careful to put the same amount of gel/water in each vase.

Just because 'it can be done' doesn't always mean it's going to look any better.
Much preferred to just color the water

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