I'm going to guess that it's not the largest ever...? That would probably belong to a Giant, while this one looks like a King. He's still very pretty though. But agree with the others, a size reference would be nice.
My king was quite active back when I had him. Never saw him just "sitting there". Putting something like a coin or qtip or something next to his tank would be nice. Then we can see how big he really is. He looks a bit fat. Kings are a bit bulkier I know, but that THAT much. lol