HELP HELP

Question
QUESTION: Hi Lynda! I am in bad need of fish advice. I inherited a freshwater tank-about 20 gallons and have kept ok care of it except the algae. I have NEVER had a problem in the past 6 months with any of the fish. 5 days or so ago i went to the fish store in china town and bought "algae eating fish" they attach to the walls and everything and have cleaned the tank quite nicely. yesterday i noticed the tetras were all in a group at the top of the tank. I noticed one of them was "banging" his head around. Today i gave it a closer inspection and the five of them were covered in white spots and they are no longer see through. i quarantined the worst one and he died 20 minutes later. the other types-one pair of each and i'm sorry i dont know what they are. they are bigger though, silver dollar size and silver in color. the other guys are quiet and gray in color with what looks like a moustache hanging from their face? sorry for the akward descriptions. the quiet guys are now racing around the tank like mad men.i have put in fungus medicine because the box had pictures of what looked like fungus. now reading this blog the ich sounds like it may be the problem? i'm really unsure and don't want my fish to die. the tetras are turning gray. the "algae eating" fish may have something to do with this? what can i do to help them?
thank you!
Stephanie

ANSWER: Hi Stephanie,
Never treat fish without knowing first what is wrong with them.  I don't know what medication you put in your tank, but I would do water changes to take this medication out, and then give them a treatment with "ick cure"  Use half the dosage, as tetras are very sensitive to this medication.  These parasites must have come in with the fish you recently bought.  This is why it is always better to quarantine new fish before putting them into the main tank. When fish are rubbing against things in a tank, and have white spots that look like salt, it is Ick.  You will have to treat all of your tank.
Hope that this will solve your problem, and that they will recover.
Lynda

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QUESTION: Thank you Lynda! Just so i'm clear...replace half of the water tonight? i've read other answers that said to put aquarium salt in the tank? it is after 8pm and i wont be able to get ick medicine tonight, should i do anything else to the tank that could help them?
thank you,
stephanie

ANSWER: Put 4 teaspoons of aquarium salt that you will have diluted.  What is the temperature of your tank?  What medication did you put into your aquarium?  I will wait for your answer.
Lynda

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QUESTION: Lynda,
The tank is currently at 74 degrees. i have two heater in to keep it that warm. it recently dipped to 64 and i had to add a new heater to warm it up. tonight i have cranked it a bit more. with the main heater at 87 degrees it keeps the tank 74. not sure why, maybe an old heater. the fungus medicine was "fungus clear" it is an alka seltzer like tablet that disolved quickly and a couple of drops of "Maroxy". i just tested the ammonia and it is 0ppm. the pH is between 7.4-7.8
thank you very much. i have added the aquarium salt.
stephanie

Answer
The temperature went down very very low, and this could be a reason why you have problems.  Never bring the temperature up fast when heating a tank.  This should be done 1 degree each day.  I think you brought it up too fast, and this is the reason why your fish are banging.  There is nothing you can do tonight.  Leave them in the medication, and put your carbon back in, it will remove some of the medication.  Tomorrow, make a 50% water change, and buy some quick cure, using half the dose.  I'm afraid that you will lose some fish....not because of the ick, but bringing up the temperature too fast.  Also, you water is alkaline, and alkaline water does not agree with tetra fish.  They live in acidic waters.  I wish I could help you more, but for now this is all you can do.  I'm sorry.
Lynda