I only have the one albino BN pleco that I got with the koi angels from a local breeder, he gave it to me for free. But, I have some bad news to report as today I lost one of my koi angels probably due to high nitrites as I checked the water with my API master test kit and it was way high. In a matter of ten minutes he went from swimming and falling down on the bottom to just laying down and died. That's my fault though, because I was overfeeding them and I'm going to cut back a lot. But I guess you learn. I did a 60% water change after that so I think that should take care of a lot of that. I also replaced one of the filter cartridges from my filter, it's a top fin 60, and left the other one in. This tank has been going for 3 weeks now. I still have the other 5 koi and 2 marbles, so I think I should still be alright on numbers for forming a pair. I was also wondering, could I get by with a water change every 2 weeks at 50% once this is established? Right now it's only been 3 weeks so I'll do a water change every week of about 33%.