white tip shark catfish

Question
I got a tank, aprox. 30 gallons from my work they were not taking care of it or the fish so I offered to take it home. it was very dirty you almost could not see through but I cleaned it very well I only used hot water and a scrub sponge.
The tank came with six fish and forgive me but I do not know the names of their species so I will attempted to describe them. 3 were a sort of goldfish, 2 were zebra danio, and one was a very HUGE sucker fish. I bought a new filter for it and a thermometer that also heats the water I bought several others, 2 more zebra danio, a shrimp, 3 red with black fins almost the same body as the goldfish, a bala shark, a yellow and black fish, and a silver tip or white tip shark.
they have been fine for over a week but I have yet to see the white tip eat he just swims around the tank very fast and in a complete circle (meaning following the entire edge from end to end of the tank) now when I got home today the water was murky not too bad but noticeable, I noticed that the filter seemed to be backed up and checked it it seemed it needed to be changed so I did but before I did I noticed that the silver tip was swimming slow and 3 out of four zebra were pale almost whit and the silver tip had white things on it it almost looked like tiny tiny little white grains of sand.
My questions are:
  what should I feed the silver tip, can you tell me what the white stuff was, and is there something wrong and if so what?
any help would be greatly appreciated, I have really grown a liking to these little guys and so have my kids I would hate for anything to happen to them.
Thank you SO much
Brandy

Answer
Dear Brandy,
Congratulations on your new tank rescue! I know how it is to see fish that need help.
Well, you have a few problems that we need to try to solve with your fish.
First of all your tank is going through a complete cycle since it hasn't been maintained  for a long time things were not good when you rescued the fish.  You had to clean things up a bit since the tank had been so neglected. Now your tank has to go through an cycling period to establish the good bacteria that helps control the ammonia and nitrite build up in the water caused by any fish waste or leftover food particles.  It takes several weeks for  this cycle to complete. You could help it along by buying a container of bacteria at the fish store and adding it to your tank. There are different brands. You may need to add this more than once since you may need to add some medication to your tank and medications will kill some of the bacteria you are trying to establish in your tank and therefore you will need to help replace it.  You will also need to do small frequent water changes, maybe changing 1/3 of your water, at least every other day for awhile. It would also help you to know if the ammonia and nitrite level is becoming unsafe for your fish and you could check this by purchasing a water test kit from the fish store.  The reason you will really have to watch your water very close is because you have alot of fish starting out and there isn't enough bacteria established yet to handle the load of waste they will produce and if you don't help in controlling it they will die from ammonia poisoning.  It can be controlled if you really are careful. If the ammonia gets too high immediately do a 50% water change to try to bring it down.  It will also help to use a water conditioner that helps to eliminate ammonia, nitrites and nitrates along with removing chlorine and chloramine, whenever you do a partial water change. I've used Amquel Plus or Prime. There is also a product called Ammo Block that can help if suddenly you have an ammonia spike and need to reduce it quickly. Also, be sure to check the temperature of the replacement water to make sure it is the same as the tank water.  Very lightly feed you fish the next few weeks since the more you feed them the more waste will be produced. Also, be sure not to give them too much food at one time and remove any uneaten food after about 5 min. They can get by with being fed maybe once a day for now.  You will need to give your sucker fish algae wafers or even a slice of zuchinni since he won't have anything to eat.
You should'nt need to change your filter for several weeks. If it looks dirty rinse it off in aquarium water placed in a container.  The reason for this, if you rinse it in regular tap water, any good bacteria that has established itself on it will be killed by the chlorine in your tapwater. You need all the bacteria you can get right now.
The specks you are seeing on your fish could be ich.  You need to treat this. Sometimes fish will get this as a result from stress and being in water that the temperature has fluctuated too much.  It is treatable but it takes some time. There are many theories as to how to treat this. Raising the water temperature to at least 80f-85f helps to speed up the treatment and elimination of ich. Remember if you raise the temperature you also have less oxygen in the water and you may need to also use an air pump with an air stone to help make sure your water is aerated enough. You also need to treat a little longer after you see the white spots disappear from your fish since it is still in the gravel. I use a product called "Maricide". It seems to work but there are a lot of others. It is up to you which you think is best.Water conditions along with ich will cause your fish to not feel like eating. Sometimes, with ich they can get other problems such as fungus so be sure to observe them just in case this happens, It doesn't always happen but it is possible.
As for the feeding of your fish, try to lightly feed them at this point. Good quality flakes will work for most of your fish now and algae wafers for the  the sucker fish. Some of your other fish will also like the algae wafers since they also like vegetable type foods. Later when everyone gets better you could also try feeding other foods such as frozen brine shrimp,shrimp pellets or even other pellet foods. If your fish seem to be feeling better you can try small feedings now but not too much or too often since your tank still has to get established.
I am going to send you some websites so you can read more concerning the ich and medicating your fish.  There are different ways and opinions on how to best treat it.  Some fish can only be treated with half the dose of some medications and some can't use but just certain types of medications. Be sure to not over medicate since some of your fish will probably only be able to use half the dose, such as your shark type fish and your sucker fish.  Also, if you think some of your fish could be tetra fish, they will also need less of some medications. Just be sure to read about which medication would be best.  Some medications also suggest removing carbon from your filter since carbon a can filter out and dilute your medication and cause your fish to not be getting medicated properly.
It is possible that you could loose some of your fish since your tank is trying to cycle and there is a possibility of ich on some of your fish.  Hopefully this won't happen.  In the past I have had some really sick fish and they have pulled through it all but you really have to stay on the water situation and make sure you are doing everything right.  It will get better and you can save these fish and give them a better life than they had. Just hang in there!
Here are some websites that will explain ich.
http://www.fishjunkies.com/Diseases/ich.php
http://freshaquarium.about.com/cs/disease/p/ich.htm
Here is a website on cycling tanks
http://freshaquarium.about.com/cs/biologicalcycle/a/nitrogencycle.htm
Be sure the check your water as soon as possible for the ammonia level, with a test kit. It could really high at this point of cycling and be extremely hard on your fish.
Best of luck with you fish!
Hope this helps,
Karen