Problem with aquarium

[Nelly]

Hi. I need your help please!! Don't know what to do. My cichlids are swimming on the top gasping for oxygen. I have an air stone and wave maker.  Water test, amm-0, Nitrate-40, Nitrite-0,Hardness-25(very soft),Chlorine-0,Alkalinity-180,PH-7.8,Temp-82.  Thx in advance. Did 25% water change...

[AllFishNoBrakes]

I’ve never personally dealt with that, but I would consider turning down the heater. The higher the water temp, the lower the dissolved oxygen. Consider adding an additional air stone if you’re able to. 
 

When you did the water change, I assume you used dechlorinator?

[Tony s]

What kind of cichlids. There is a vast variety.

and how new to the tank are they 

[Nelly]

Hi. I just lower the Temp to 78. After water changed, I used Prime.  I have some Haps and Peacocks. Around ten. The biggest is around 3 inch. I have them for about a three wks. I noticed the problem two days ago. ??

[Tony s]

First thing I see. Your haps and peacocks are going to like very hard water. Probably at least 240 and higher. Now, depending on where you got them, they may not be used to your water yet. If they come from harder water, putting them in softer water can create osmotic shock. The softer water will try to pull the extra minerals from their bodies. If they’re already adjusted, they may be fine. But there may be a limit to how much they can adjust. The African lakes are incredibly hard with high ph and high kh. 
 

not to say this is the cause of the current issue. But maybe.  You could probably go as low as 76 on the temperature. 74 is the low limit. Your parameters look fine. Maybe another air stone. 
 

your dosing of prime is on the low side of directions? Prime can deplete the oxygen if used in too strong of a dose.

[Nelly]

ok. Thank you very much for taking the time and for your advice.