Tap water

[DoMa]

I've been using tap water in my sps dominant tank for 15 years which has a heavy bioload of fish.  Nitrates average 15ppm and Phosphate around .1 with the use of vodka and lanthanum.  I get that people believe rodi is the only way but I do question how many of them actually have tried a window and compared results.

[Michael Damron]

I think the issue lies in part with what makes up the phosphates and nitrates. Austin water report is publicly available.. I can't understand half of the stuff that is on it, I just know that it's probably better off out of my tank and that only requires a $100 rodi unit.

[Timfish]

I have systems maintained with RO/DI and systems maintained with tapwater.   What's critical IMO is water changes to reduce the labile and refractory DOC in systems*.  Whether RO/Di is used or tapwater is used, from what I've seen, doesn't matter much.  In my 2nd thread on fixing a system over run with algae tapwater was used.  In the  system below ATI ICP tests showed PO4 was about .3 mg/l higher in tapwater used for water changes than in the system.

 

 

See these links for more info on how DOC causes coral disease and death:

"Coral Reefs in the Microbial Seas" This video compliments Rohwer's book of the same title (Paper back is ~$20, Kindle is ~$10), both deal with the conflicting roles of the different types of DOC in reef ecosystems.  While there is overlap bewteen his book and the video both have information not covered by the other and together give a broader view of the complex relationships found in reef ecosystems
https://www.youtube.com/watch?v=-R2BMEfQGjU

Maintenance of Coral Reef Health (refferences at the end)
https://youtu.be/dGIPveFJ_0Q