Hi there ,70ltr tank set up dec 04 have now got a sick male guppy who likes to lay on the bottom or hide in the woods, not eating good but now and then looks and acts normal for about 10 or 15 secs then slows down again been with me for 4 months 10 to 15% water change every week glowlight tetra`s and zebra danio`s o`k any one help. thanks.