They're Really Growing... But Still Alevin

I was very relived to walk into my classroom this morning and find that the Rainbow Trout were still alevin.  They didn't yet need to be fed and all were still alive.  However, I did start to notice that some are looking a little differently than others.  Below I have a picture of what I feel is a healthy Rainbow Trout alevin.  You can see that the yolk sac is still attached, but is becoming smaller.  You can also see tiny fins moving when you look at them closely.

There are a small number in the tank that concern me.  It seems as though their yolk sacs are twice as big, but are transparent.  I can still see two tiny orange yolk sacs inside the transparent bag, and the alevin seem to have trouble swimming around.  In fact, when I got these two out of the tank to take pictures of them to post on here, one of their yolk sacs just fell off!  I was really heartbroken because I knew that meant that he or she had passed on.  I'm adding pictures of them below.

I'm going to call Don Thompson from Trout Unlimited after school to see if I need to remove these fish, or if it's just a natural deformity.

Also, Mr. Joe Chavez from Central Office came to visit with Ms. Leffler's fifth grade class this morning.  We had a great time and tested the water quality, and the kids showed a great understanding of what was going on.  Their predictions made me start to wonder about my own learning with this project.  Thanks for coming, Mr. Chavez!