I am rehoming my brothers livestock. He has neglected it for a few months since he is moving. I have my tank cycled and ready so I went over to test his water parameters. 0 ammonia,0 nitrites but the nitrates were off the chart. Way off. The API test sample was ruby red. Over 160 by a good amount. I did a 50% water change and brought it down somewhere between 80 to 160. Fish showed no signs of stress before the water change. 10 duboisi and 4 petros are in the tank now. How far down should I get the nitrates before I can safely bring them to my house tank which is <20 nitrates ? Any dangers in doing large water changes to get it down to normal limits in his tank ?