Way off topic but quickly - this is typical for all such multilingual families in the USA and I don't think it is stubborness. It's hard on a child, it's work, and the child is naturally looking for a path of least resistance, just like electricity or water or adults haha... If she/he goes to an English school, it seems the only way is to speak to the child at home only and exclusively in Greek or Russian (one day Greek, the other day Russian) and only respond to the child when she/he speaks the right language for that moment, otherwise ignore. This is the only thing I know of that worked for such families. Otherwise, the child will never take to other languages except on an extremely limited, ever diminishing scale. Of course, the parents must spend time with kids, read to them in their native language, have them read, discuss, joke, play, communicate with grandparents, uncles and aunts, same-language friends, etc.Will do. It’s hard to keep the Russian going with the kids. My 5 year old went to Russian daycare so was fluent in Russian, English and I was teaching her Greek. Since starting English school she refuses to speak Greek or Russian. Reminds me of my stubbornness as a kid.
Back to the big grey scary aimara... I wonder why you don't give it whole thawed fish. It is cheaper than hikari, could be as convenient and quick with some planning, and will get it to grow faster I'd reckon. I'd not cut out the hikari completely though, no-no.