RODI + Nitrates

[jwiley3493]

Hey all just getting back into the hobby after about 15 year hiatus. I started up a 36 Bow front tank. Set it up 4 weeks ago. I purchased a Liquagen 5 Stage 75GPD RODI (pic attached). Running Well water through the system.

Tank has been very high in nitrates (around 20 ppm) with little budge on a daily basis. I added a bottles worth of API Quick Start nitrifying bacteria.

Could all be from the normal Nitrogen Cycle. But, my nephew has a 13 gallon freshwater tank and all his fish died from ich. So I went and helped him clean the tank and then we added 13 gallons of the RODI water. A week after letting it run he added 2 fish and they both died within 24 hours.

The reader on the rodi says its taking in 264 TDI and putting out 0 TDI. But I was curious and ran a nitrate test on some freshly made RODI water. Came back at about 8-10 ppm.

The non-live rock I put in has turned white and the purple colored live rock is losing its color.
Read that this could be too much light (total light exposure is about 9 hours of blue, 6 hours of white). So I'm leaning more towards nitrates being the reason.

Can anyone help identify what's up or what I should do? Thanks

 

[Woodyman]

Are you using the stock filters on your RO/DI?

If so the first recommendation I would have is for some higher quality DI carts.

Spectrapure, BRS, and others all make high quality DI cartridges. It sounds as if your DI cartridges aren't truly getting you down to the "0" TDS your looking for.

Another option could be another carbon block. Depending on the composition of the nitrate, without getting to involved in some water chemistry, carbon will pull certain nitrate compounds from the water.

But again my first change would be for a higher quality DI cartridge and if you can add a second DI filter housing/cartridge as well so that the water goes through 2 housings of DI instead of only 1.

 

[Timfish]

What was the nitrate reading of the well water? If it was really high some nitrate may be making it through. As far as your nephew's system I'd think it was just too new and the RO/DI thinned out the fish's sline coating or there was a problem with the fish when you got them. 8-10 mg/l nitrate shouldn't be an issue for most freshwater aquarium fish.