that clam still doesn't look happy, they like a lot of light so you may want to consider redoing your rockwork and putting the clam directly under your halide (thats what that is right??) Keep in mind that clams will quickly drain your calcium on a tank that small so if you want to see them happy and healthy you are going to need to either change your water more frequently or dose something. Also take my advice, get the hippo out now. As he grows and he will grow fast, he will add a lot of bio load to your tank and on a system that small with that little rock your setting yourself up for a crash (I speak from experience). Sell him and the fluvals and invest in a good hob skimmer and a little more rock, then work from there. You can always buy another one later on down the road when you have the space. Just my 2 cents