Angelfish Acting Strange

[Shima2510]

Hello,
 
We have had our tank for about two or three months now and everything was fine. We made sure the water was 100% ready to get some new fish and we have very slowly been building our tank up. It is a 30 gallon tank. 
 
We bought our angelfish a good three or four weeks ago and everything was fine, one is a striped colouration and the other is a Koi colouration. They are the smaller variety of angelfish. When we got them they were fine swimming around, eating fine and the other fish left them alone. Now however the Koi coloured is acting strange. It sits in the corner or along the top of the tank, not really doing much, it will swim a bit and then stop but it is not as active as the Stripey one. He has been like it for a four days and his mouth is pointing towards the surface. We are extremely worried about the little guy. We were wondering if it could be lonely. I have looked everywhere for an answer but haven't found one. We do regular 20% water changes about twice a week. 
 
Please if you have any idea what could be wrong with him or have any advice we would greatly appreciate it. 

 

[Ninjouzata]

to TFF!
 
Answering these questions may help figure out what could be going on.
 
1. Water parameters. (ammonia, nitrate, nitrite, PH, temp', Hardness etc)
2. A full description of the fishes symptoms.
3. How often you do water changes and how much.
4. Any chemicals and treatments you add to the water.
5. What tank mates are in the tank.
6. Tank size.
7. Finally Have you recently added any new fish?
 
A picture or even video would be good to show the behavior. Also how did you cycle the tank?
 
I doubt I can be of much help but did want to get the answers to those questions for someone with more experience in angelfish.
Some fish just have different personalities, one may be lazy and the other quite active. Do want to make sure there isn't anything wrong though.
 
And if I'm not mistaken, there is no smaller variety of angelfish.

 

[attibones]

 
And if I'm not mistaken, there is no smaller variety of angelfish.

 
This is correct. "Small variety" typically means juvenile.
 
OP, have you noticed any aggression? Angels can be aggressive towards each other, especially when they are maturing. They will bond with only one mate and often times kill any other angels. Most people get six or so and hope that a pair forms and then rehome the rest. You may be experiencing this.