.start-container
{
/*	background: transparent url("img/White-christmas-light-background.jpg") no-repeat fixed center center / cover; */
	background: url("img/White-christmas-light-background.jpg") no-repeat fixed center center / cover;
}

.akvarium
{
    background-color: #005aff33;
    width: 100%;
    padding-top: 54%; /* For keeping aspect ratio */
    position: relative; /* If you want stuff inside of it, you need this. */
}

.akvarium .tile {
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
}