Practical Sailor, a non commercial testing group in the US, did some comparitive studies on this subject and from what I remember, they found no benefit from adding antibiotics.
rafted alongside a swedish doctor a couple of years ago, and he swore by this approach. he used streptomycin, courtesy of the swedish nhs. certainly his boat launched at the same time as mine had much less fowling. however, what chance of getting your gp to prescribe you a kilo or two?
interesting alternative approach i saw being used in the channel islands was not to antifoul at all, but to dry out twice a season, spray the underside with a strongish solution of domestic bleach, let the boat stand for an hour to kill all the nasties and then a quick powerwash. seemed to work, and was cheaper and easier than antifoul.
It works! I'm told it started in Norway where people breeding
salmon started mixing the fish antibiotics in their paint.
I got a few overdated bottles from a cousin vet and the boat
was clean all summer after mixing in the paint. I didn't do it
again as antif paint still is available, but what mixes will be
the result of too environmentally friendly antif paints?
Don't know about antibiotics, but I have heard plenty of stories of our American cousins mixing chilli powder with their antifouling. Apparently it does wonders for the boats bottom but isn't much fun on a tortilla!!
