I have realised today that my filter isnt pumping out water so much as it was.  If the fish got in the path of the flow coming out they would go flying but now its nothing like that, i have had the tank a couple of months.  Is this a sign the sponges need changing? and also which ones do I change?
Or this is a sign its packing up
 
Thanks
				
			Or this is a sign its packing up
 Thanks
	            