.fishtank	{
    background-image:url("sturgeon.png");
		margin: auto;
		position: absolute;
		top: 0; left: 0; bottom: 0; right: 0;
		height:272px;
		width:499px;
		background-size:499px 272px;
		}
  	
  	
    @media only screen and (max-width: 480px), only screen and (max-device-width: 480px) {
        .fishtank	{
    				background-image:url("sturgeon.png");
        		margin: auto;
        		position: absolute;
        		top: 0; left: 0; bottom: 0; right: 0;
        		height:136px;
        		width:249px;
        		background-size:249px 136px;
    				}
    	}