Fish survival dilema

Question
QUESTION: Hey there Karen,
This is going to be long, mine is the weirdest case of fish keeping. It started with a gift, a Kissing Gourami that was surprisingly solitary. Being the first time I went to the local Aquarium store, and explained the concerned fish' supposedly aggressive behavior (had seemingly killed 13). He suggested a mate, to pair up and we got a female. Being newbies, we had a really small tank, (dimensions - 12" by 10" by 21"). We eventually added a couple of Koi. The store keeper consented to that too. Gradually another Koi was added and the female Gourami died, and the space constraint was more than obvious. We got a new tank with dimensions(36" by 12" by 15") seems to work out to 28 gallons. Leaving some room at the top, it has about 22.44 gallons of water. Now about checking ammonia levels in the tank or other parameters was not something I was aware of or informed. Have recently read this information online. I changed the gravel when setting up the new tank to sand; not too fine, and introduced the fishes. To add to their woes there were many more additions. A female kissing Gourami came first. Then 2 red fin sharks. A day later, 2 albino sharks, 4 Mollies, and 2 angel fish.
If that was not enough the tank was not even a  week old, so no time for bacteria to develop(something I read online). Then the death toll started. Having treated the water by storing it for 12 hours and de-chlorinating it we lost the angel fish. then another. Then the female gourami, and a red fin shark and a molly. Then a Koi(which seemed healthy too) and then Mollies again. Yeah a molly did give birth to some litters yesterday but I doubt if they will survive as the rest might eat 'em up. The store guy came and said the temperature change is hurting them and maybe I should put in a heater(yes I didn't have one, because I did not know that one was required). All fish have white spot and phin rot as he says. The heater is on and the medicines are in, but there have been a couple more deaths, (the remaining Mollies and the first kissing gourami).
'Am sorry if this is too ambiguous or too little of the necessary information. Still grabbing the ropes I realize. But if you could help. Of the five that remain, a couple of koi, 2 albino sharks and 1 red fin, wouldn't want to lose them. Please help.

ANSWER: Hi Animesh,
I think water changes are your best friend at this point. I would immediately do a 50% water change (make sure to pre-treat the new water with dechlorinator and make sure its equal in temp to your tank) and I would repeat these water changes for several days. You'd be amazed at how water changes can make fish feel better and help tremendously with tank problems. You also need to confirm for sure if your fish are sick or not, because they'd need treatment right away for either of those disease, white spot or fin rot. Why not look here for a picture of Ick-
http://cichlid-forum.com/articles/ich.php
-And for finot-
http://www.aquariumlife.net/articles/fish-diseases/22.asp

Those websites will also let you know more about treatment for white spot and fin rot. But I can't recommend anything right now until you are 100% sure that's what your fish have. Unfortunately your tank is very overstocked. I would say the most sharks that might be able to live there is the 1 redfin. The other two species would grow far too large.

Best of luck with everything, sorry about the bad news...
Karen~

---------- FOLLOW-UP ----------

QUESTION: Well apologies for the late response. Was trying to arrest the situation in my aquarium. Seems to be working for now though.  And yes the links helped too. My fish seem to have both, Ich and fin rot. Only the butterfly koi seems to be suffering from fin rot, and even that is improving.
About the water change, had done that already, after posting my first question, albeit 25% only. then the treatment began and even on the site you linked me to, water change was advised against during the medication time. So, refrained after that. Have 5 fishes now, and the red fin looked the worst. But, she's recovering. The flaky ich spots are off and I guess the parasite is in the final stages of reproducing. So, added a bit of NaCl, non-iodized of course, as the aquarium guy said. Had read it someplace, so did it. Hope shall suffice. Now, what is the period before the parasite can be assumed to have died or gone? A change of medication is alright or advised against? 'am using something local, seems to be working, but not approved. Was planning on acquiring a recommended medicine. Should I?
Thanks again.
- Animesh.

Answer
Hi Animesh,
Well, if your fish have both ick and finrot you'd be best off to treat with an antibiotic and a anti-parasitic medication. It's actually advised that you should always use an antibiotic along with the parasite treatment whenever your fish have ich. This is because it guards against secondary infections due to the wounds opened up by the ick parasites already present. A good combination is Maracide (made by Mardel) and Maracyn-two (also made by mardel) both these medications are made to be used together and are safe. If you can find these medications you should be fine using them. Just make sure to do a 50% water change and gravel vacuuming before treatment. Even though the medication directions say not to, water changes are very important before medication. This is because organic compounds in the aquarium can severely neutralize the effectiveness of a medication and cause it to not work properly. So a big water change before a medication is a -must-. And thereafter is best too, both to relieve stress on the fish and to reduce the parasitic/bacteria count in the water. Doing a 50% water change everyday is not harmful. Just redose with your medication(s) your fish will be better off for it, trust me.

Medication needs to be in the water for at least 14 days in order to be sure every last parasite is gone.

Best of luck and if you have anymore questions, feel free to write again,
Karen~