Holy crap! I have been using 170ppm TDS water!
 

So got my TDS meter since I was very curious about what TDS water I have been using for the past year. Turns out to be 170ppm! Holy crap! No algae issue or anything till now with this water. My 20 gallon was literally algae free and I used to do 50% weekly water change. My new tank is having diatom on the sand but not sure whether it is contributed by the tapwater or not since my 20 gallon just had an initial bloom and that's it.

Sheer luck or TDS is just over-rated concern.....I wonder.

TING TING TING! Start the debate!

IMO, TDS isn't the debate. After you add salt, your TDS is through the roof. The concern, at least for me, is that with tap water, you don't know when it changes or potentially becomes contaminated in some form. The key to a successful reef is consistency, and RO water adds to this consistency. On a typical day, all things appeasing the reef gods, tap water is perfectly safe. Just not the best. There's really no debate here, just preferences on tank stability and willingness to take risks, however small.

I've had bad luck with conditioned tap water generally. However the biggest thing is your maintenance schedule. I have no doubts whatsoever that you had no algae problems with a water change schedule like 50% a week. Thats crazy! lol.

On my very first reef tank ever, I had color and algae issues even with a 2 X monthly water change schedule. When I changed to RO water, my softies colored up and algae went away. Call it luck? Timing? No idea lol. But I always like to use a good old RO just in case.

I also noticed on my brothers tank (he is using tap water with big als tap water conditioner) that when I switched his brand to my good old 'prime' it made a difference on regular glass cleaning.

I live on okanagan lake and use water right out of the lake with a tds of 125 and and ph of 8 and have for years and have had 1 algae bloom over that time but i am in to deep this time so i am going to put in an ro unit with no di for the spring and summer months and not in the winter because in the winter water is crystal clear same as summer but spring with run off causes some cloudiness but i think maybe the mineral in the lake also helps and 1 example is that red pipe coral grows like rats

Usually when I talk about water contamination, I'm referring to a year I lived in Kelowna and the entire drinking water distribution circuit was shut down due to toxins in the water. If someone had done a water change that day before the emergency was declared, I'd guess they'd lose their whole tank. It doesn't happen often, but it does happen. The Kelowna sewage treatment plant discharges directly into the lake, and while the water coming out is top quality, if there were an accident, the lake would be contaminated. The cost of RO is small compared to replacing everything in the tank :)

So true lol.

Theres no words more true than "be safe or be sorry" in this hobby.

I am up stream of kelowna and in the deepest part of the lake and all the water sample people from the government that i talk to says it is the best right there are very few homes and all of Vernon sewage gets treated then irrigated onto the hills then ran though mother natures giant biological filter unlike Victoria's

The Kelowna plant is one of the best in the world, and I've drank water out of the outflow. In fact, they were breeding trout in it last time I was there. But...what if something went horribly wrong?? :razz:

The water intake has a 6" grate filtering it before the chlorination stage, keeping out larger ducks -lol

So basically, RODI is mostly like an insurance and just making sure all the contamination are taken out (if any) before they get into the tank. So, if my understanding is right, RODI is "highly recommended" rather than a "necessity". ;) Some reefers need to change their perspective :razz:

RODI unit is definitely not expensive compared to the cost of this hobby. But what intimidates me is the amount of water wastage. I don't have gardening or anything where I can use the waste water. Plus since its a rented house, wasting water is restricted in the contract. I was actually thinking of starting to by water from stores. Anyone knows where I can find "RODI" instead of just "RO" water?

I get 7-9 TDS out of my kitchen sink and don't use any kind of conditioner and let the water sit overnight with a powerhead and heater. I've yet to have algae - except in my planted tanks, it was a battle I suffered for a long time despite every effort and made me shut it down, afterwords I realized that I should of probably be using RO water.

So far in the marine tank, I haven't had any algae issues - but I do have an rodi system, that I don't use, but have some ro water stored in case of an emergency. I don't know, it's a fail safe thing for me.