rkum070

I though plants may be a problem so i took a number of them out. There isnt too many plants in the tank now so it shouldnt be a problem. In terms of pH, it is about the same (6.5-7). I think the problem might be the filter not being cleaned? I bought it at the start of the year and havent cleaned it since?

I have a 130 litre tank (35 gal) that is filtered by a 60 gallon external filter. All my fish are at the top of the tank as if gasping for air? They seem to really be struggling, even my pleco sprints to the surface and back. What could the problem be? 1) My 130litre tank has, 2 YOUNG t-bar cichlid, 5 neons, 12 cherry barbs and one bristlenose pleco. So the tank is understocked and overfiltered. 2) I dont think it is amonia levels as i have never had this type of problem before,the tank has been running for 3 years now. Plus to remain on the safe side i did two 20% water changes, one on saturday and one today. 3) My filter output is aimed towards the surface of the tank to cause light ripples in order to oxygenate the water. Again i dont believe their is a lack of oxygen but i dont know? PLEASE HELP