Hes probably getting all he needs. I'm asuming you are shelling the peas?
If hes a bit fussy , try blanched cucumber. Put in a small container with a bit of water then zap till the water just boils. this should also make it sink. Its obviously not quite as good as fresh veggies but the plecs seem to enjoy it more especially the babys as its easier to eat and digest.
And personally I wouldnt go down the garlic route but that only my personal opinion.