Anyone use pure distilled/RO water? If so, steps on prepping please!

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Look It Up
Apr 21, 2011
Rhode Island
Hi everyone,

Does anyone use 100% distilled or RO water for their FW aquarium? Due to some weird fishless cycle happenings (short background info below if interested), I was using spring water to finish my cycle. The brand I was using only sells in 5 gal jugs and I''m having a hard time lugging them up the stairs. Also not knowing how much minerals, etc are in different brands of spring water I want to be more consistent. I'm going to purchase an RO unit at some point but for now I'm going to switch over to distilled water. I bought RO Rite powder to reconstitute the water with minerals, etc. I'm getting fish this week so I want to change the tank over to the mineralized distilled water today so I can monitor it for a few days and make sure PH stays stable.

So, how do you prep the water? I have an 18 gal bucket. I was going to put the distilled water in, heat it and aerate it (how long? the PH out of the jug is 6; I aerated 1 gallon last night and after a couple of hours PH rose to 6.4 where it's stayed for 12 hours now). Then mix the RO Rite in (any thoughts on how much? I know the bottle has mixing info, but any tips would be great).

Also: when I do water changes (probably 50% per week), how do I measure the powder to get the levels the same as the tank water? I'm guessing it's just trial and error at first?

Any tips, info, etc would be extremely helpful. :thanks:

Background info of why I'm using distilled water if anyone is interested, but not directly relevent:
Long story short: I tried fishless cycling two different tanks and had no or very little movement in both after 4-7 weeks. After the first tank failed I broke it down, returned it, threw everything away in case a contaminant or something got into the tank without my knowledge, and started fresh with a 20 gal aquarium (new filters, decor, etc). After adding two seeded filter pads and sponges, ammonia was dropping very slowly and no other movement at all. The only thing I hadn't changed from the first tank to the next was my water source (was using tap water). I changed over to spring water, added another seeded filter and my tank fully cycled in three weeks (nitrites spiked then dropped, nitrates climbed, ammonia fell to 0 after each redose). So, I'm sticking with not using the tap water!
I was actually gonna use rodi water on my daughter FW tank today since it needs a PWC and I had to pick up some for my reef tank anyways. I don't see why with adding the right chemicals for balance it wouldn't be perfectly fine
I just use tap water. No sense in wasting all that money for ro/di water unless you have a reef tank (imo). Are you using an ammonia source to dose the tank up to 4ppm when cycling? If you go higher than that it typically will stall out for a couple of weeks until you do a pwc. Have you read the article on here about how to fishless cycle?
And my rodi water only costs $0.40 a gallon. Cheaper than distilled or any other- and where I live you can't use tap water (sad to say) it's way too messed up
Thanks everyone.....

@ Jlsardina -- so any tips on aerating and prepping? I was going to fill my 18 gal drum with the distilled water and let it heat and aerate for a few hours. Then add the RO Rite, test the PH/Gh/KH and put it in the tank (does it need to sit and mix further or can I add it right in since it's a FW tank)?

@ Rhino - Thanks, but I can't use tap water. I think my water is too clean. Or at least something is either missing from or added to it to make the BB not thrive. After trying to fishless cycle two tanks in the span of 3 months and only after changing the water source did the tank cycle, I'm going to say something is up with my tap water and I''m not using it. Since spring water varies and I want to be consistent I figure starting off with distilled until I can get an RO unit would be best. Believe me I wish I could use the tap water, it would be a lot simpler and less expensive but, given the issues above, it seems the tap water isn't working out. And yes I'm using pure ammonia and dosing daily. 2+ weeks ago the cycle finally completed (0 ammonia after 24 hours, 0 nitrite, and levels of nitrate rising) and I've been dosing every 24 hours to keep it active. And yes I've followed Eco's guide and he has helped me immensely through the process (it was his idea to try changing water sources, which ultimately cycled the tank).

Thank you both!
I always treat FW overnight at least and then add the next day. So what I do is let it sit and get to the right temp and put all chemicals in it and maybe aerate it over night. Then for a cleaning the next day I will siphon the tank and then scrub and add water. IMO the longer time allows the chemicals to take affect. But that's just me.

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