I dont know whats wrong with my Male Betta

Question
QUESTION: I've had my Betta fish for about two months.
I bought him with the best intentions, I purchased a 2.5 Gallon Tank with A filter, A cartridge and  light. I even bought him toys to go into his tank and rocks to go at the Bottom. Along with the fish, I purchased Betta fish water conditioner. I've never used tap water until about two days ago. I always used gallons of spring water like "Deer park etc." He was happy, healthy and he always greeted me when I went over to the tank.
I was over feeding him at first, but I stopped and everything was perfect. I recently Bought A thermometer for the tank and a new castle for him to sleep in. Two days ago I changed his water because the cartridge was worn out and dirty And it caused the tank to become foggy. I never took the cartridge out completely though. I cleaned it and returned it to the tank... Today I noticed that he wasn't swimming as much and he kept hiding. Also at the top of the tank there is bubbles and they were pink.... as if he was maybe bleeding? I looked at the cartridge and it was also pink...My first theory was that maybe it was thermometer... but it showed no signs of leakage or anything.... His scales look kind of furry and there is also fur like things around his eyes but one of his fins looks as if it can't move anymore.
I figure the furry stuff maybe from the cartridge that is broken and needs to be replaced, but I don't know. he is very still and will barely swim, unless it's to hide. I have had the same toys in the tank for a while.. so for this to suddenly happen is beyond belief. The only things i changed were:

1 . I used Tap water that I let sit for hrs+ I added the conditioner to it

2. I added a plastic castle for him.


Could he have gotten hurt?
Can I fix him?
Will he die?


3. I added a thermometer..

ANSWER: Jasmine,

 I do not think it is the water. Tap water is better for them than spring or bottled water. I also do not think it is the thermometer. I would guess it is the plastic castle that you put in. Only put aquarium safe objects in the tank with your fish. Plastic is never a good idea to put in with your fish. They can release toxins that can kill. I would remove him from the tank, and clean it out very good. DO NOT use soap of any kind. Just clean it with very hot water. I would just remove the filter. With a tank that small you don't need one plus Betta's do not like them. I would guess that the castle was painted either red or pink and having it the water caused the colors to bleed. Once you have cleaned everything. fill his tank back up. Make sure you use a water conditioner before you put him back in. Make sure you are testing his water and doing 25% water changes weekly. You did not mention his heater. He is tropical and needs his water to be 82 degrees at all times. I hope we got to him in time. Let me know how he is doing.

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

QUESTION: Thank You for replying to me.
Actually, the castle I got him, was in the Fish Aile.
And It's not Pink or red, it's white.
I called Pet smart, they told me to come in and get medication that will treat Bacterial diseases called Betta-Fix. (Due to Skin Shedding)
I don't have a heater at the moment, but I plan on buying one soon.
I did however, boil his water a bit and let it cool down to a good warm temp before placing him back into it.
He is very much alive... but still looks terrible.
I am going to buy his medication asap.

ANSWER: Jasmine,
 
 Be very careful with both Bettafix and Melafix. They are both very potent and if not used perfectly, they both will kill your fish. As for the plastic castle in the fish department, I would reconsider buying from them. Plastic is NEVER ok to place in a fish tank. Do not boil the water you are going to put him in. Also, the new water has to be the same temp as the older water. If it is a little cooler its ok but it can NEVER be warmer. If it is the fish will go into shock. Since you do not have a heater the water temp WILL get too cold for him. The fluctuation in temperature is not good at all. NEVER treat a fish with ANY medication unless you are 100% sure what the problem is.His skin is NOT shedding. Fish do not have skin nor can they shed. His slime coat is depleting. It is because of the toxic water. How warm was the "good warm temp"? Do you have a thermometer to know what the temp was? Is there a way that you can attach a picture of him so I can see what he looks like BEFORE you treat him with a deadly medication?

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

QUESTION: I can take a Picture tomorrow, And yes I do have a thermometer.
Also what do you mean by toxic water?
And where did the pink or red stuff come from?
I do have a pic of that.
And I only have a camera phone, which may result in horrible quality, but I can try to get one to you.

Answer
Jasmine,

The toxic water was the water he was in with the castle. You said everything was fine until you put the new deco and other things in the water. Plastic is toxic to fish. Therefore the water will become toxic and very quickly. Thank you for trying to get me a picture.