Does it have to be 0 TDS?

Meh.. people act like everything is all or nothing... I ran a reef tank with no additives straight out the tap for 3 years and everything survived just fine. By the time I found out about TDS I found mine was coming out well over 200.

So 2-3... yeah I don't believe it's the end of the world.

 

Thank you for the comments Mr. Bill. I realized that a lot of people are not successful with tap, that's why I got RO/DI unit. This is not about tap water Vs RO/DI water.

Again, back to my question, will 4-5 ppm actually have same problem with tap? is it proven that this is the case for failure or is it just precaution?

I wanted to actually change my cartridges/filter, but the manufacturer actually told me that I shouldn't even have to worry about 4-5. Once it hits above 10, then I need to change them.

 

WOWWWWWWWWWWWWWWW.......... over 200 ppm??? are you serious? ;D You got algae issue at all?

 

OK, my direct answer would be that it's mostly precaution. How harmful 5 TDS can be depends on exactly what it is, and we don't know that answer, so it may never be "proven" to cause failure, regardless. But again, there's always a fair chance that it's mostly harmless (i.e. 5 TDS of assorted non-metallic minerals would have no effect).

 

Makes one wonder sometimes, doesn't it? But like with everything else, I prefer to err on the side of caution when giving advice.

 

Mr. Bill, Thank you for your "direct" answer ;D. I am going for it 4-5ppm.

 

I mean in those days, I had all kinds of issues. I was looking for decoration on the wall pretty much. But I had corals and fish that lasted all the way through that tank and into my big tank. At that point I knew what I was doing and they started to grow and thrive. But the tank in reference is the tank in my avatar. That's all non filtered straight out the tap water and was kept up on 2 t5s and water changes and flake food and that's it! I didn't buy an RO/DI filter till after this tank was broken down, I never even used a de-chlorinator. I can only imagine the success I would have had in that little tank if I had used proper techniques and water though.

 

The reason for RO/DI and for 0 TDS is consistency. Tap water quality changes. The blend or sources can change with no notice, Joe Contractor could dig up the main down the street and cause a cross connection. A storm could blow through and the treatment plant changes their chemical treatment to keep up with EPA water quality regulations. This often changes the pH and even dissolved oxygen levels in the water. The big thing is they do not have to warn you or notify you so you could be making up a big batch or water for a water change and have no idea its bad or different!

With RO/DI you get the same water each and every time and you yourself control its quality, you don't depend on anyone else. When you strive for 0 TDS you don't have to worry about weakly ionized substances that escape through exhausted DI resin such as silicates, phosphates and nitrates. These do not register well on a TDS meter so are often much higher than you imagine and you cannot use hobbyist grade test kits to test the ultrapure water.

Better safe than sorry. RO/DI is very very cheap insurance for the hundreds or thousands of $$ you will have invested in your reef tank.

 

Mine has been 20-40 for the last couple of months, until i notice it and replace the cartridges, i didn't had any problem at all, but i prefer to keep it under 10.