I'll scrap the bag idea. As for the size of the kubs, four are about 2 1/2" and one is just 2" TL. It is one of the larger ones who is suffering.
This is an excellent idea. I'll be doing this as soon as it is daylight.Another way you can try to handle the problem with ammonia: massive w/c using a mix of fresh water (25%-50%) and dirty water from an established tank. After the parameters equalize, you can safely do nearly 100% W/C.
(I did this once with 100% daily changes, feeding a 10g quarantine from 125g which only benefited from extra small changes; worked fine until the cycle stabilized).
