A few points to ponder...
A previous post mentioned Allycin, the "active" ingredient in garlic extract that works like an antibiotic.
As with all antibiotics, they are designed for targeted, profilactic use, not systematic supplemental use. Over-use is the common error, which reduces efficacy. Any parasite which may be inhibited by garlic, may form a natural resistance if it is used daily as a food supplement.
There are irrefutable examples of garlic stimulating feeding response, and promoting recovery from ich. But the smart move is to use it only when it is indicated -poor feeding response, signs of ich onset, etc... and then only sparingly for a short period of time ( a week to ten days) in small doses (a drop or two per feeding.) It is not the panecea, and it a period of treatment does not work, then more garlic will not work.
Melafix and/or hyposalinity protocol are effective as well. Melafix is a tea tree extract that simulates the tanins found in litoral mangrove regions. As soon as I can find the link to melafix treatments, I'll post it. It can be found at:
www.thereefweb.com under the discussion section.
The proper way to prepare food is to let it thaw to room temperature in the garlic solution, ensure it soaks well and is thoroughly mixed in and semi-absorbed before feeding. Some data suggests that only internally absorbed garlic produces the healing response. Who really knows?
Excess garlic pollutes the water, and may be detrimental to other little critters in our filters.
My vote, there are effective ways to treat ich, that involve no chemical additives (hyposalinity) and others that are a little more natural and non-polluting (melafix) which are certainly worth further discussion...
Nellie
