I hope someone can help me.  One of my guppies died yesterday--he looked fine, and then the next time I looked he was gone.  Today, another guppy almost looks like his body is sagging a bit, and his orange tail is now a quarter black.  I did a water change, checked all water parameters and they were all normal.  I added some Melafix, for the past couple of days, but it doesn't seem to be working.  I just did another water change (2nd today) and it seemed to help a little bit, but I don't think it is a good idea to do water changes every couple of hours. 
I don't know what is wrong with my tank. Like I said, all the parameters (nitrite, nitrate, ammonia, pH) are all normal.
Please help! I don't want to lose any more fish.
Thanks.
				
			I don't know what is wrong with my tank. Like I said, all the parameters (nitrite, nitrate, ammonia, pH) are all normal.
Please help! I don't want to lose any more fish.
Thanks.
 
	             
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		