Hi guys, I was just feeding my 4 zebra danio when I noticed that my rescue one (Lucy, the one missing an eye) has a large lump on her head/back. My mum said she had noticed it there a while ago and thought it was just where she was growing old, should I be worried? She has been behaving totally normally. I have (hopefully) attached a video and a bad quality photo, but they move so fast! They are due a W/C on Sunday, and if need be I will double check all the test results but last time I looked (last Saturday) they were 0ppm ammonia, 0ppm nitrites, and just below 20ppm nitrates. The temperature is approximately 26*C, and its my 20 litre tank (gosh... right after I post this I need to update my tank information, it's not accurate any more). Thanks guys!