As far as I’m concerned, the bottom line on fertilizer comes down to “Pretty much any
complete formula will do. Use it regularly and sparingly”.
If you want to get a formula that is intended for orchids, that’s great - and they may be better for the plants - but not mandatory.
As far as additives are concerned, you had better know what you’re getting and how you’re using them.
Mega Thrive is an excellent way to stimulate new root growth in rootless plants, but, in my opinion, should not be used as a regular treatment, for a few reasons:
- Regular overdosing trace elements can really screw up a plant nutritionally, or kill it.
- The chemical is toxic.
- Any plant treated with the stuff is immediately toxic to birds and mammals.
Synthetic hormone treatments (KLN, Superthrive, etc.) can be useful for root recovery and general stimulation, but can be overdone, leading to flower deformities and stunted growth. Plus the stuff chemically degrades rather quickly, so you have to be sure to get a fresh bottle and keep it cool and dark.
Natural kelp products vary over the map, based upon species used and processing. My stance here is pretty well known, but you might take a look at
this article.
As far as probiotics are concerned, I think they are a subtle “boon” to growers that few consider. Pretty much any of them is better than none at all, but the more complex the blend of species, the better.