It is perfectly possible and safe to use a 100% melaleuca in any volume of water. You just vary the concentration volume. This is made into a dose by measuring out sufficient to "treat" the system.
Quick question for anyone (you must have some handy)
What is the concentration of melaleuca in betta fix?
What is the prescribed dosage?
Overdosing is prescribing more of anything into any volume.
The volume of the recipient tank is inconsequential. Careful measurements.
I most certainly would use mela fix in any system. If I had a pond id have pond strength only, I'd use that. I'm not buying several versions of the same thing at different concentration.
(slightly off topic I used pond strength dechlorinator because it was cheaper, you use less for a similar price by volume therefor it is cheaper long term.) I use double strength malachite green, I use that in all of my tanks from 45 litres up to 750 litres. Same bottle. No problems. It's sold for large volumes but I've had no trouble using it in much smaller volumes, careful precise measures.
You can use what you want, it is not my place to dictate where and how you spend your money.
(The most annoying thing about this whole thread,
my auto spell keeps writing meal fix)
Considering this,
"I've never lost a cycle because of medications. The Pima and Melafix aren't really medications anyway - they are more remedies. I personally have next to no faith in them. All too often people use them when they should be using real medications. Of course that's not to say that they don't work at all, but there are definite limitations to what they can do."
You seem to be quite passionate about the whole affair, it seems to me that you are changing tracks slightly throughout, it is somewhat confusing. You're telling me what I'm telling you. Please take the time to re-read this thread.
(Looked at the link, for pimenta, I guess that's in pimafix?)
One for melaleuca would be good.
Patent US5882647 - Aquatic animal treatment method and composition containing cajeput oil - Google Patents cajeput oil patent.
Ta da!
Also species of fish is important, something called tolerance. Even within a species group tolerance can be quite different, that's why some fish die first.
Now let's talk about species sensitivity. Not all species are equal. Need I say more?