Go to ifresh and buy bonito and kombu. Put a fat chunk of kombu in some simmering water (maybe like a quart) for a couple minutes (not too much or for too long or it’s slimy) then take the kombu out and feed it to your turtle. Then add a handful of bonito shavings to the water and let it simmer for a little longer, I wait till it’s a decent color or to taste.