Hi all - I am very grateful to all those who've researched, experimented and posted to share this information. I don't actually keep any "monster" fish or frankly any middling fish, but as a healthcare professional I've frequently needed to recommend probiotics to my human patients and have therefore been a little puzzled by the dismissive attitudes I've heard being expressed by fellow hobbyists re use of probiotics in home aquaria.
This thread clarifies things enormously since it allows me to understand both the point of view that dismisses massively over-priced and questionably effective aquarist targeted products, while explaining how to obtain good results by applying a little science-based know-how rather than marketing hype.
As my previous experience with dosing probiotics is with humans and other mammalian pets benefitting enormously after (very necessary but) prolonged antibiotic medication, I was researching how to apply the same broad principle to fish-keeping when I stumbled across this thread. While my first thought was to have something in the medicine cabinet to follow up antibiotic treatments, I'm now really excited to use these as part of my aquarium maintenance. I see it as a significant enhancement to re-creating a natural eco-system in miniature because surely many of these bacteria are present to opportunistically colonise in the wild whereas our sealed tanks and sealed canister filters actually prevent such "real world" balance?
In humans the same principle applies in that most folks with a good diet that includes fruits and veggies have no problem re-colonising the gut after antibiotic meds - the probiotic bacteria are everywhere - but someone who's living on junk and frozen food is almost inevitably going to get some problems.
Anyway I joined up to express my thanks and (having read the entire thread) ask again for a recommended product that's available in the UK at a reasonable price? For example I've seen some products that would do the job (I think) but they're going for £45 ($60) despite being septic tank/domestic products. Not the $10 deal I was hoping to find . . . I will continue to search of course, but if someone UK based has already found the solution?
Sorry - my first post here so can't post links to provide examples
cheers