Yikes! Glad to hear you did not wind up "sleeping with the fishes".
Yes, between all the fish and the garlic, the odor is rather noticeable. I do all the mixing out on the patio. My wife GAVE me my very own food processer just for this purpose.
Right or wrong, to this point I've been using canned seafood, peas, and pumpkin. I prefer the seafood packed in water, but at times I have used some sardines packed in olive oil. I don't know if the brands matter, but I have used Crown Prince and King Oscar. Once we had some big cans of sardines in tomato sauce. I wasn't sure that would be good, so I hosed the sardines off before I mixed them in. Rather than garlic salt, I have used McCormick's Garlic Powder. However the batch I just mixed up a week ago has 10 oz (~7% of the mix) of garlic cloves from our garden, chopped up. Seems like no matter what I put it the mix, they can't get enough of it. This has never caused a water quality problem for me, but I should note that I mainly feed this in an 1800 gallon pond with established filtration. The effect on water in a smaller tub may differ.
In my showa thread from last year at
https://www.koiphen.com/forums/showth...owa-spawn-2015, check out posts #28, 33, 70, 96, 98, 106, & 132 where Wombat provided lots of recipe and feeding tips.
By the way, last week I mentioned that I was not seeing any ginrin, but now I am starting to notice a small number of ginrin, perhaps on about 10% of them.