I have "lost" 2 x zebra danio from my tank. I have another zebra danio, 6 x platys, 3 x glowlight danio, 3 x dwarf rainbow fish and 3 a golden zebra loaches...all seemed fine. I went missing 5 dayas ago another today...is this usual behaviour, dont know if they were breeding, my water is fine. I f I cant find them and they are dead inside some of my decorative media is there a risk to my water balance. I have a 160 litre tank.....7 weeks old...ammomia/Nitrite 0, PH 7.5 and Nitrate 10.