Possible inflammation on Angel fish

Question
QUESTION: Hello,
I hope you will be able to help me. This morning my albino cat fish died very suddenly and while I was taking it out of my tank I noticed little red spots along its fins (which looked like blood but I am a novice to fish keeping so I may be wrong.)How ever I also noticed that the edges of the fins on my Angel fish have reddened too.However, the gold fish and the platies (I apologize if the spelling is wrong) do not have this.I am afraid that this sudden reddening of the Angel fish fins may be a sign of disease. If you could help me find out whether my Angel fish are sick and if so a remedy, I would greatly appreciate it!
Thank you.

ANSWER: Hello,
I would like to have more details.  One thing I do know is that Goldfish should never be mixed with Angel Fish.  Angel fish need 80 - 82 degree water.  There is no exception to the rule, and Goldfish need cool water.  Angel Fish thrive in acidic, neutral water, whereas Goldfish need alkaline water.  The size of your tank would be important for me to know, as it could be overstocked.  I would like you to test your water for ammonia.  If you have ammonia in your water, do a 50% water change using a good conditioner such as stress coat, or AquaPlus.  The next day check to see if there is ammonia in your water.  If you still have ammonia, do a 25% water change again.  Do this until your ammonia level is down to zero.  Ammonia is the number one killer of fish.  Water changes every week of 25% is a must with all fish, and always syphon from the bottom to pick up any decaying food.  I am thinking that you have too many fish for your tank.  Angel Fish need lots of room - one angel fish would need 15-20 gallon tank to be happy and healthy.   She is out of place right now.  I think that this is due to bad water conditions, also water that is too cold for angel fish.  Little catfish need 78-80-82 degree water too.  They are tropical fish.  It could also be bad diet.  There is no cure except changing her habitat, which means no goldfish, water temperature 80-82 degrees, clean water, no ammonia, or nitrates in the water.   I'm sorry, but this is what happens when we mix fish that should not be together in a tank.  We cannot go against nature.  Fish get sick, and sometimes die.  Check you water, and if you have anymore question, just ask me. I will try to help you as much as I can, but for now either the goldfish have to go, or your Angelfish.  If your pet store manager is a nice guy, he would gladly take some back, and give you a credit.  Write back to me with more details...the size of your tank, your ammonia level..what your feed your fish...how many platys, and goldfish you have...this is very important for me to know.
Lynda

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

QUESTION: Thank you for your help, unfortunately I will have to give away my goldfish since I have Platies too and don't want to jeopardize my goldfish by giving them a bad home.
I have a 28 gallon tank with 3 Angel fish, 2 platys,1 cleaner fish (I don't know its real name) and 5 goldfish (which I will be giving away.)
I feed them flakes and frozen peas. As for the ammonia levels I will follow your instructions as soon as I am able to buy an ammonia test kit.
Thank you again for all your help!

Answer
Hello,
Do not wait very long because ammonia will kill your fish.  Do a water change now, as I am sure you have ammonia in your water.  That was way too many fish for a 28 gallon!  One goldfish needs 10 gallons just for himself, Angel Fish too...Diet, and good food is so important to fish.  A good flake that has good vitamins is very good for Angel Fish.  They must have blood worms now and then ,and frozen brine shrimp.  Daphnia is good for Angels, and all fish.  Don't forget to feet your Pleco  ( cleaner)  They too must have food, and the pet store sells pellets just for them.  Without food  they starve to death.  Vary their diet, keep their water clean, bring the temperature up slowly, very very slowly....one degree every two days.  Bringing the temperature up to fast could kill your fish, so do this slowly, and your shouldn't have any problems.  When fish live in good water conditions with enough room to swim, and good food to eat, they hardly every get sick.  With the cost of curing fish today, it is better to feed them right, keeping their living space clean, then spending money on curing them, never knowing for sure if they will make it.  Fish are like us.  We need vitamins, and space.  We wouldn't like to be confined to a small room for the rest of our lives, would we? and sharing it with other people who couldn't speak our language, can you imagine?  Wouldn't that be horrible?  Same goes for fish!!  
I hope you will be able to save your angel fish, and I am always here to answer any questions that you may have.
Lynda