themodernchap
Seedling
I think the best waterchange system is the Reefloat. Not sure if I'm allowed to link to their site but it's very well thought of in the UK reef scene. You fill it with fresh water, link it into your system and it slowly circulates the fresh water into your system. Then you disconnect it and drain it. They reckon that you waste about 5% of the fresh water but I think it is well worth it for the convenience. It's fully automated you just set it and go do something else, it beeps when full mixing has been achieved. It can also premix salt water for reefs or I suppose it could re mineralise RO for planted tanks. UK made and excellent customer service too.