Help Please

Hi everybody
I have had three zebra danios die in the past month and now there is another one sick. They are in a 44 gallon tank and I change 25 to 30 percent of the water every 7-14 days. Checked nitrite,nitrate,ammonia,copper and ph and they all look fine.
The fish start out by looking very swollen in the belly area and there not pregnant I know the difference on that anyway they start out that way then they start getting very skinny pretty quickly and they also look pale and they stop eating as well. I have the others that look fine on medicated food hoping that will keep them from getting sick until I find out what is going on and how to treat it. I thought it might be wasting disease or some kind of parasite that they got from feeding them worms but I'm not sure what would be the best medicine that will not mess up the biological filter bed and that will not harm my chinese golden algae eater. Please if someone has dealt with this disease let me know the best way to go.
littleT

Hi everybody
I have had three zebra danios die in the past month and now there is another one sick. They are in a 44 gallon tank and I change 25 to 30 percent of the water every 7-14 days. Checked nitrite,nitrate,ammonia,copper and ph and they all look fine.
The fish start out by looking very swollen in the belly area and there not pregnant I know the difference on that anyway they start out that way then they start getting very skinny pretty quickly and they also look pale and they stop eating as well. I have the others that look fine on medicated food hoping that will keep them from getting sick until I find out what is going on and how to treat it. I thought it might be wasting disease or some kind of parasite that they got from feeding them worms but I'm not sure what would be the best medicine that will not mess up the biological filter bed and that will not harm my chinese golden algae eater. Please if someone has dealt with this disease let me know the best way to go.
littleT
Sorry on posting it twice was trying to post pictures will try and fix later time to eat....Sorry again

Any fish died of bent spines.
Being really skinny is old age, internal parasites to fish tb.
Signs of internal parasites are.
Being skinny or bloated.
Long stingy white poo, or clear mucas poo.
Red inflamed anus to enlarged.
Worms prutruding from the anus.
Sometimes a bent spine.

Hi Wilder
No bent spines
Have not notice the poo
No red inflamed anus that I could tell
Have not seen any worms from anus
The one that is sick now has very little time left he now is laying in the plants and on top of the decorations in the tank and not hardly breathing at all. It wont be long now.....
I will keep a close eye on the rest hopefully it was just old age. I have had them now for about 2 yrs. I think too that it could be a parasite. Do you know of any good parasite medicine for treating this condition? Any that will not harm my golden chinese algae eater or my biological filter bed.....

Treat with Internal Parasite Guard, Pipzine, Disco-Worm, Trichlorfon or Fluke-Tabs as well as a medicated food to prevent a bacterial infection.

Thanks very much wilder!
Poor little fish he is a goner. He is now laying on his side and breathing heavily.....I put him in a breeder net but his time is almost up.
I will keep an eye on the others and if they start getting sick I will buy some of the meds you suggested and I will keep feeding them the medicated food. Thanks so much for your help.

Sadly yes he sounds like he's on the way out bless him.
Good luck with the rest.

He was just laying in the plants on his side breathing really hard so I put him in a breeder net but I felt bad watching him suffer so I put him in a bag in a cup with water and place him in the freezer poor little guy....I hate doing that but he was just suffering. I heard that was the best painless way for the fish...Thanks for the luck

Thats the worst way putting them in the freezer it can take ages for the fish to die.
You just get a jug of coldwater and add icecubes till the water freezing cold, then add the fish to the jug, it should take about 20 seconds for the fish to die, but best to leave the fish in the jug a while just to make sure the fish passed on.