The little fish have done us proud - we bought a shoal of 13, 14 years ago and they have been happy in our 60l tank. However, we've been down to 2 for a while and today, the second to last died. I only have one left. Would it be kinder to kill it? I have heard about oil of cloves being the kindest way. I don't want any more fish. WWYD please? TIA