Hey Brad, Sorry you feel like your getting hammered. I hope thats nobodys intetions here. It seems like your focused on P04, and might be forgetting about alot of other things. While many fish can survive at elevated rates of p04, there are so many other particles that get by the sediment, and carbon filter that can be very harmful to fish. The RO filter is the work horse of a RO filter. Thats why they call it a RO filter instead of a Carbon or sediment block filter.
We do know tap water varies on a daily basis. And can carry pestisides, zinc, copper, iron, floride, And the list goes on and on. Here is a governmental link stating what actually is found in tap water, And states that over half the polutants in tap water are not even regulated. Unfortunatley we dont have a TDS meter that gives us a readout of exactley everything found in our waste water, And weekly 250 part water sample test would be out of the budget for most hobbyist. So all we can do is use our best judgement and try and do whats best for our aquatic creatures that we've come to love so much. They are helpless and rely on us to take care of them.
I will insert this brief paragraph for those who dont want to read the link. :
EWG's analysis of tap water testing from 42 states validates the public's concern about tap water. We found that between 1998 and 2003, water suppliers collectively identified in treated tap water 83 agricultural pollutants, including pesticides and chemicals from fertilizer- and manure-laden runoff; 59 contaminants linked to sprawl and urban areas, from polluted runoff and wastewater treatment plants; 166 industrial chemicals from factory waste and consumer products; and 44 pollutants that are by-products of the water treatment process or that leach from pipes and storage
http://www.ewg.org/tapwater/findings.php
What we do know is that tropical fish can be very very delicate to chemicals, metals, poisons, ETc found in tap water. If P04 was the only concern , many people might not have RO filters today.
With RO waste water, You are subtracting the polutants from the clean water, and flushing out the toxins with the run off water . Therefore as some test have shown, waste water can be more toxic than tap.
If you want to try and quarantine your fish with this type of water, It is your decision and no one has the right to judge you for that. But in my opinion it is futile to try and debate that RO waste water or tap water is harmless and causes no ill effect to aquatic life. Some fish may survive in this type of a invironment for a period of time, others wont last a day. And theres really no way of knowing what all the toxins are doing to the fish. If they die, we say bad water, If they live we say good water, But in reality, how can one really know?
I think one of the reasons that gets people fired up over threads like this is because many are animal enthusiast. And they just cant understand, why one would use RO waste water, when they have perfectly good water to use.
Many people may argue, Ive done it so it must be OK. But to be perfectly honest, many people would probably eat a whopper, fries and shake ,rather than a healthy meal. Then after the arteries are clogged , they have high blood pressure, over weight and diabetes , they come to the conclusion, Might not have been a good idea.
I admire that you are one to look for true facts and have a true interest in this hobby. I hope the article might have some facts that might help you. One thing about this hobby, It doesnt usually take very long to find out what works and what doesnt. And either way we learn along the way.