Tomato has parasites!!! I've been worried about him since I got him (not eating as readily as Lettuce), so I put him in a quarantine tank over night and brought a fecal sample with me to work (I work for a Vet, so no that is not weird!). I can't remember the name of the worm (very common in WTF I'm told), but luckily it's not zoonotic and easily treated with dewormer. Lesson learned: poop has all the answers