New tank, 1 sick fish

Question
QUESTION: First of all, thank you for helping my poor fish.  I am new to aquarium keeping, my only previous experience keeping a betta in a bowl for the past year.  We got our kids a new 10 gallon aquarium kit for Christmas, and I was going to let it cycle for a couple of weeks empty, until I read that it needs fish in it to build up the good bacteria.  So, we put the betta in it with a plant and a plastic cave, then wanted it to look less empty, and newbies that we were, we went and got two black mollies and two otos on the advice of the pet store clerk that they were all compatible, as well as some live plant bulbs.  A couple of days ago, one of the black mollies developed white patches that I think are fungus, clamped fins, shimmies, and has been pretty much residing on the bottom of the tank.  I've been doing 2 gal water changes every two to three days, complete with water conditioners, but yesterday I added 1 tablespoon aquarium salt, a water heater (which I found out when I brought it home does not allow adjustments, but keeps the water at 78), and then a fungus clear fizz tab.  The mollie does seem to be doing a bit better, though when I used my new test strips last night the nitrite was high at 3.0.  Alk was 40, Nitrate was <20, hardness was 75, and pH was 6.8.

Now for my questions:  (1)Will all of the fish do well with salt added to the water, and how much should I add?  I am mainly concerned about the otos, since I really couldn't find anything to say online.  (2)Do I need to do water changes more frequently until the nitrite goes down (say every other day)?  (3)The fungus fizz tablet from jungle labs says I can readminister in four days.  How does changing the water affect this timeline?  (4)I also purchased ammonia clear from jungle labs, but I am uncertain whether I should use it, as it sounded like it was similar to the water conditioner I was already using(Start Right from Jungle Labs).  (5) Should I get some ick treatment and use it as well?  The package said to use at half strength for scaleless fish, which I gather the otos are. (6) Should I be concerned about any of the water quality levels, and what can I do about it?

Again, I thank you, and my fish thank you.

ANSWER: Hello,
Mollies need salt, and alkaline water.  Your PH is way to low for Mollies, it should be up to 7.8 8.0.  The Molly needs salt, in order to survive, be healthy and happy.  You cannot add salt because the Oto cannot take salt.  Otos should never have salt in an aquarium.  
Whenever starting an aquarium, you must make sure first that there is no ammonia, or nitrates in your water before adding a fish to it.  Never, ever add a fish to water that isn't established.  You can buy these small test at the Pet Store and they should be number 1 in your fish cabinet.  Ammonia should be done to Zero, and Nitrates should be safe.  The only way to get ammonia and nitrates out of your water is to do water changes everyday until you get it out of your water.  There is no magic solution in a bottle to remove nitrates or ammonia.  The only way is water changes with a good water conditioner such as "Aqua Safe" or "Stress Coat"
Your Molly has fungus due to bad water conditions, and he is also stressed because of the low PH.  No Molly can live in acidic water, with no aquarium salt in the water.  You will have to make a choice here, either mollies or otos...You do not need ick treatment, your fish do not have ick.  
Your main concern now is getting your water chemistry right, and curing your Molly.  This is a catching disease so the tank will have to be treated.  Now we have a problem with the Otos...we must always be careful when medicating Otos.  First you must make a choice on which fish you are going to keep so I can help you. Write back to me as soon as possible so that I can tell you what to do.
Lynda

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

QUESTION: Hey, the follow-up worked today!
Thank you, Lynda, for your help.  I have read of some people keeping otos in a brackish environment (by brackish I mean a little aquarium salt added to the water).  But I have absolutely no experience in keeping fish, and I hate for the poor otos to not be comfortable if they don't like salt at all.  Truthfully, I don't care for the black mollies, now that I've had them for a week and a half, but I don't want them to suffer and die, either.  

I have started 2 gal water changes every day, using water conditioner according to directions just as I have for the past year, and the nitrite is going down, and the sick molly seems a tad better, less shimmying and the white patches have decreased.  The reading I took today after the water change was: NO3 <20, NO2 2.0, GH 75, KH 80, and pH 7.2.  This is what it was yesterday after the water change as well.

The fungus treatment said I could reapply in four days, but I have been changing the water every day (twice since I added it) so should I reapply now, two days later?  I also had to take the carbon filter out to use the medication.

Now, what do I do next?  The fish I really have to keep is the betta - he's the one we've had for a year and enjoy watching (the only one the kids have named).  Will it do well with the otos?  I do have an empty five gallon tank, but no filter or space for it, and a betta bowl, so I can separate them temporarily if I need to, and maybe find a new home for the mollys, because I really only want one tank for now.  Will my betta do well with the otos (he seems to be ignoring them now), or does he like a little salt as well?  

How do I establish the water in a new tank?  I had read in several places that the tank needs a fish, and its waste, to develop the organisms that keep the water stable, but then, as I found out, the fish is exposed to all the contaminates and becomes sick.

To think, this all started because I didn't think it was good to keep a betta in a bowl!  I realize I made several big mistakes, adding so many fish to a new tank and trusting a pet store clerk to know which were compatible to each other(she said she had them all together in her tank at home), since it was really hard to find anything online, but right now I just want to get them healthy again.  Please let me know what my next steps need to be.  Thank you, Jen

Answer
Hello,
What you have to do is get those mollies cured, bring them back to the Pet Store, and get a credit or buy food instead of fish.  Also I would see the Manager of this store, and tell him about your experience with the Mollies.  This was terrible advice to give a customer.
Now that your fish are in the tank, you must make water changes until you have no more ammonia, and nitrates are safe.  When starting a new tank, it is wise to buy an old used sponge at the Pet Store.  A used sponge is full of good bacteria.  A sponge is good for a long long time.  When cleaning your filter, always clean the sponge in the same water temperature as the water in your aquarium as to not kill the good bacteria.  When your tank is established, and you have checked your ammonia, and nitrates, and all is safe, then you put a fish in your tank, and not before.  One fish, and check your water one week later to see if the chemistry is still good.  If it is, you add another fish, and so on...
You are in a bad position right now.  Your must do water changes and cure your Mollies which is next to impossible.  You must get your water chemistry right, then cure.  The worse part is fungus is a catching disease.    
Try to get your water chemistry right, then cure your mollies...if you lose them, well you can blame the vendor.  Mollies do get sick in fresh water, they do need salt, and a high PH.  Otherwise, they get weak, and sick, as you can see.  You must think of your Betta right now.  He needs clean water with no ammonia, and nitrates or he will get sick too.  He is now in 78 degree water, you cannot put him in an unheated tank, as the temperature would go down quickly, and this could kill your betta.  The same thing goes for bringing temperature of water up too fast.  This should be done one degree every two days to be sure that the change would now hurt fish, or shock them.  The same applies to adjusting the PH, we do this very very slowly.

A 10 gallon does not hold many fish.  If your Betta is getting along with the Otos, then no problem leave the Otos in.  The Otos live in the same PH as the Betta.  Normally the Betta is always the last one to enter a tank.  I have never experienced any problems with bettas, only if they are betta females in a tank, or if he is being attacked by other fish.  Of course small fish are food to him, so this is to be avoided.  He is a loner, and prefers to be alone.
Below is a little more information on bettas that I think would help you...

A betta should be fed Betta pellets, Betta flakes, Daphnia, alternating each day.  He should have bloodworms once a week as a treat.  He should also fast one day a week, and on that day he should have a pea, and nothing more. ( You cook a frozen pea until it is well cooked and tender.  Remove the outer layer, and cut it into tiny pieces.  Feed this to your betta, one piece at a time making sure that he eats the pieces, and that they do not fall to the bottom of the tank.)  The pea cleans out his system, and keeps him from having Swim Bladder Disease. He should have 2-3 small meals a day...one day pellets, next day flakes, and so on.  Example:  2 pellets for one meal.  His tummy is the size of his eye, we must always remember this.
Water changes every week are important for your betta with a good water conditioner.  (Stress Coat, or Aqua Plus, they also sell a conditioner specially made for bettas)
Betta do not live healthy happy lives in small containers, vases, and tanks.  Their lives are cut short, they get sick, and die.
The longer the tank, the better.  I know they say that a betta can live in a small containers, but this is untrue.  He may live, but will be very unhappy, and will have a short life.  Five gallon tanks are the smallest in my book where the betta would be comfortable, and live a happy life.  You did well to get him a 10 gallon tank.  His tank should be heated.   Water should be 78 - 80 degrees.
If I were you, and was content with my betta, I would not add anymore fish.  Tetras live in groups of six which a ten gallon tank would be to small to house.  Platys, and Guppies are 3 females to a male.  They are live bearers, eat their young, and are always harassing the females.  If you decide to put them into your tank, they might nip at your betta.  His long gorgeous fins are an attraction for many fish.  You could put in one male Platy with 3 females, or one male guppy with three females - your choice.  One or the other.  You could also just put in 2 female platys... See how it goes, it may work, and it may not...each fish has their personality...If you do add other fish, do this when your water is perfect, one fish ..then one week later another, and so on.  Always check your ammonia, and nitrates every week, even if your water is established, and do 25% water changes every week without fail, and you should be okay.
Hope this helps
Lynda
Hope this helps
Lynda