using old tank water in new tank??

Just in the process of switching over from a 55gal to a 90. Is it better to use some of the old tank water in the new tank. Does it help with Ph stability at all?

 

if you old tank was stable then use that water. if it had nasties in it then only use a little of it... if you have corals though, it is best to use the old water because it will be less of a change for them = less stress

 

+1 to dingo's post. Goes along with everything I've ever read on the subject

 

My 55 is starting to get some cyano on the rocks and sand bed, so is using that water going to start a bloom in my new tank? My 55 was tap water. I have just purchased a RO/DI unit so I won't be using tap for the 90. I will be using some of the old sand though to seed my new sand.

 

since its all tap i would discard it all then. if you put a little bit of sand in to seed it will be fine

 

If it was tap water I would definitely recommend throwing it out. use ro/di water and some sand from your 50 to seed the 90