Hi, I got a new rat on Saturday at the usual place I get rats, and he was fine at the store, but when we got him home he was breathing hard. We put him in his new tank with paper shreds (the store had him in pine bedding and the travel box he was put in had pine bedding), and he started sneezing a LOT. It died down after the first 24 hours and he hasn't breathed hard since Saturday, but then we put him in the big rat cage we have after seeing him looking miserable and stressed in the small 10 gallon tank. I should note that he's about 2 or 3 months old, but is rather big for his age (he's probably the size of a 4 or 5 month old, but his head, ears and feet are still large compared to his body like a 2-3 month old). The move stressed him a bit at first, but now he's more used to his new cage and has even popcorned a few times, with his speed even picking up (he was sluggish at first when we got him out of the box). He seems to be fine when he's playing outside his cage and sneezes less outside of it. However, the sneezing continues, he still washes his face delicately, and sometimes there's clicking and occasionally mucous-y sounds along with the red stuff around his nose, but it seems to be getting a bit worse. It doesn't help that his poops stink, possibly from switching abruptly to Oxbow Mouse & Young Rat food from an unhealthy mix the pet store provided (it was some laboratory mouse and rat food mixed with pigeon food and shelled peanuts). I started giving him fish mox last night, mixed with some apple juice for flavor, but I may have given him too high of a dose of the mox and the juice, because he spent most of the time he's usually active sleeping, and when he pooped it smelled worse. I also gave him some diluted unflavored Pedialyte, which he drank. I'm planning to clean his cage today to see if it helps his breathing, and I plan to give him a much lower dose of mox with more diluted apple juice. However, I wanted to try to get some advice before I do anything else (aside from cleaning his cage, because it stinks). I'm hoping we don't have to take him back to the store, since he's warming up to us and I don't want to basically sentence him to death there. I live with my parents, and neither of us can really afford to take him to the vet for a check up and antibiotics. What should I do?