Fish tank emergency!?

Well, by gross what exactly do you mean? If it was algae, while it looks terrible, it's not dangerous to most fish as long as you fix the algae problem, filter the tank, and oxygenate it (assuming you have an air stone or at the bare minimum a good filter).

Take the water to your local pet store, most of them test for free. :)

If you can't do that, it should be safe to put them back in.

Elaborate on what you mean by gross, if you didn't find and fix the initial problem someone can help you prevent that from happening again. :)

Also, when you say they haven't eaten, do you mean you have no fish food or they have no diet? If they have no appetite, try microwaving something acceptable for them in fresh garlic. Garlic helps stimulate appetite, and absorbs through the food. Don't feed them garlic directly though. I don't know what type of fish you have, but most small fish will accept frozen and shelled peas if you want to try that or frozen broccoli.

Good luck.

EDIT: That sucks when a filter breaks. I assumed you meant loss of appetite, but wanted to clarify. lol Try the pea and garlic then if possible. It works wonders on stimulating appetite and building their immune system. ;)

just a question are you running a light on the tank or is it near a souse of sunlight as you need to slove the problem or it will come back eg more algae. Algae needs light and gaven the fact that you state you have plants in the tank I am guessing you are leaving the light on the tank way to long each day. The 1st port of call would to be cut back on the light and you will find this will solve your algae as less light the algae will die off.

EDIT:

Alright now I know there a light there how long is it on for???? The best time frame for a planted tank is 8 - 10 hours with a light on the rest of the time no light on this should solve the algae problem

if you are already doing this back it off for a hour so eg 7-9 hours and see if help ya just got to find the right balance. If it is on 24/7 or many hours of the day it will cause algae without fail... By doing this you will find the algae dies off and ya tank stays clean.... And cost here NOTHING at all beside saving ya abit of money on ya elec bills:) a good thing for a uni student

Also to the eating thing I would not be to worry about this one as more than likely they been having a good old feed on the endless supply of algae in the tank

So long as algae etc still is in the filter and on ornaments etc then you should be okay as this would suggest the healthy bacteria is still present being though you added tonic to the water, so I'd say yes, they have obviously survived worse so this can only be an improvement.

*Congratulations on being the only student currently in profit - Drinks are you then eh? ;)

First of all they will be unhappy and get ill if you don't feed them daily. If you have no fish food at least put in a little bread for them.In the circumstances I'd check the water temperature then put them back in the main tank.