I was looking and I cant seem to find much information on increasing stability of harm(al)ine during the manske style salting process.
On my last big batch I got to one point where nice clean orangish yellow crystals reverted to dirty orange on the next manske cycle. Whatever red-orange-brown decomposition product contaminates the harmalas can clearly form during a manske.
Has an effort been done to determine what pH, contaminant metal salts, temperatures, etc. harm purity?

I'm guessing previously boiled water is preferable to reduce oxygen. Is demineralized water good enough or does distilled make a consistent difference? A touch of vinegar? That sort of thing.

I'm running a 31 gram crystallization of already half pure harm(al)ine now in which I first dissolved 0.31 grams of ascorbic acid in previously boiled water and I can at least say it did not decolorize the dissolved harmalas, it looked like 450 ml of coffee.

I dont want my crystals dirty orange-brown!

There's a lot of anecdotal evidence that the red color is oxidized harmalas. (I have personally left some harmala liquid on the counter for days and been rewarded with a red stain) I've also heard that the dye "turkey red" comes from this oxide, even though everywhere else on the internet I've looked at says turkey red is from another plant... anyways, the point is that the oxide seems to be a strong dye so it's reasonable to suspect that even very small amounts of it can discolor your product.

If you are concerned with purity I wouldn't bother, but if you want pretty crystals maybe just put some vitamin C in the liquid when you dissolve the previous manske? I doubt harmala ascorbate salts are insoluble. You could try a reduction reaction on the oxidized harmalas?

Yeah, in this round I put in some vitamin C thinking if the red is the 2N oxide it would reduce it like how it bleaches mushroom tea. It didnt tho.
I'm working towards the harmine/DHH to harmine/THH reduction with subsequent separation so it'll be fun to see if that removes much colored impurities, and then if they recur after that and in which fractions it recurs.
From the pics I've seen, THH doesnt seem to go orange-brown. The harmine likely will unless I prevent it tho.

And your right, its probably aesthetics more than anything.
But who doesnt want pretty drugs