Tap water

[NYRANGER]

I was wondering if topping off with tap water is the reason why i only achieve brown algae growth. My ro unit cartridges need to be replaced but it is on hold due to finances. Scrubber was doing fine until my ro weakened. 135 tank with 180 watts t5 lighting on a santa monica style scrubber. The scrubber has been running for about 7 months.

Thanks

[SantaMonica]

It is possible that the tap is letting N and P get in, which would be the same as feeding the tank more: Darker growth. This would just require a stronger scrubber to deal with.

Usually with high nutrients you also have the option of just waiting longer for the nutrients to be removed, but in the case of tap water there will always be more nutrients going in. So you just need a stronger scrubber now (or fix the RODI).

BTW it the DI portion that remove the N and P, not the RO.

[iggy]

May be helpful to look at differences between diatoms, brown film covering sand and brown algae due sometimes to high nutrients or low lighting.

Here is Dow Filmtec response to ammonia rejection by RO membrane. RO membranes also has difficulty with monochloramine which I read about lately.

https://dow-answer.custhelp.com/app/...rate-rejection

[Floyd R Turbo]

Wow that sucks. My tap water comes out around 60-65F and pH higher than 9.0. I didn't know that it made a difference for NH3/NH4+ rejection. Glad I'm using a scrubber.

[NYRANGER]

Thanks for all the info, much appreciated.