The pr0pioitor of my favorite LFS who is very good with fish – swears by fresh garlic – but not for wrasses - I've never found garlic to be a game changer one way or the other...In fairness I've not had too many occasions to use it.
I think though that there is sufficient evidence – both anecdotal and research based to elevate it above the “snake-oil” classification making it worthy of further investigation and discussion.
One caution though is that while many studies report “statistical significance” of results – that alone doesn't imply “biological significance”. Going by research studies alone is fraught with difficulties – they often can be suggestive, but it’s rare that they are directly on point. Generalizations made from such inferences are often poorly founded and can be flat out wrong.
“The conclusion that there is a statistically significant difference indicates only that the difference is unlikely to have occurred by chance. It does not mean that the difference is necessarily large, important, or significant in the common meaning of the word.”
As to the suggestion that garlic might cause liver damage in fish – you might be inclined to dismiss this possibility based on the lack of studies on this result. I don’t think this would be a necessarily valid conclusion.
Here are a couple of studies that might give you a little more food for thought…the first in rats – the second with fish.
“Therefore, the present study suggests that garlic with high dose has the potential ability to induce liver damage and low doses (0.1 or 0.25 g / kg body weight/day) are safe doses of garlic.”
This study leaves the question of chronic administration and cumulative effect largely unanswered, but after reading that one here’s one that’s more specific to our question:
“the damage of garlic on both liver and kidney in this work may be attributed to the relative high dose of garlic used.”
Clear signs of damage to the liver and kidneys – but no follow through as to what dosage would preclude such findings – nor the effect of chronic administration – both questions unanswered.
So some evidence that garlic could be involved in liver damage – does it apply to how we use garlic in our tanks? Maybe. It enought to temper my enthusiasm a bit – but I think you would next have to look at the efficacy of garlic in some real-world applications.
I admit I have not read many articles – but like lionfish – I do prefer some of the aquaculture studies as they tend to more closely align with what we’re trying to do. Just bear in mind that growing fish for consumption in a few months is different than keeping them long term – and maybe breading them. Just pointing out, they may be more inclined to not examine chronic exposure.
This study looks at garlic powder as a food additive for fingerling Atlantic salmon in an aquaculture setting and contrasts results with controls and other agents when treating an amoebic gill disease:
I really did not dig in to deeply on this report, but on first pass, the results aren’t that impressive, and not even that consistent, but I do like the specificity of the report.
I have no dog in this hunt – just thought I would share where I think the “garlic caution” may have originated from and at least one study that used garlic in an actual "in vivo" application. So all I can say is garlic powder doesn't look too promising for salmon smelts with ameobic gill disease - nothing more.
In the large list of studies cited by lionfish – it would be interesting to see how many assessed liver function and histology and which, if any yeilded
in vivo, biologically significant (not just statistically significant) results.
