I just wanted to say. I lost 3 fifteen year old silver dollars today. They were male and hassling our 25 year old females and causing so much stress to them. I decided to move them out. I didn't do water parameter tests on the other tank as it was running with Corries. They died within 3 hours. My tank unbeknown to me had crashed with virtually no oxygen the Corries were okay but silver dollars had no chance. I am so annoyed with myself for being so cock sure of myself after keeping fish for about 30 years not to have tested the water, rookie mistake.