TaliaLondon TaliaLondon
  • Just popping in
  • Just popping in
  • Joined: 30/12/2013 9:38
  • From London
  • Group: Registered Users Basic Membership
  • Posts: 11
  • Posted on: 14/6 2:02
Bad tap water #1
I have horrendous tap water so dilute 1/3 with RO from my local aquarium shop.

I am considering getting both HMA and RO filters as we have high aluminium, other metals, chlorine and nitrates in the tap water. I’d like to use 60% RO in my main tank. The kh would still be 5 ish so with weekly changes and monitoring kh twice a week I think it would remain stable, and I’d keep a buffering product on hand in case needed. Ph would still be over 7.

I’ve looked at filters. I’ve been told to buy filters with before and after reports but literally none I’ve found offer these. When enquiring they just say depends on your tap water so we don’t supply them, but they miss the point that when you have hard water home RO systems won’t remove all tds, and hma needs to be pretty heavy duty on metals and chlorine here.

Any recommedations or things to look for?

So far I’ve looked at vyair, devotedly discus, east midlands filters. And read reviews for many others online. Was thinking about talking to a local window cleaner who kindly helped me out in the first lockdown also but his system recommendations will probably be expensive/large.

Fishlady Fishlady
  • Tropical Moderator
  • Tropical Moderator
  • Joined: 6/7/2010 19:26
  • From Worcestershire
  • Group: Caresheets Moderators FK Supporter Registered Users Image Admin Advisers
  • Posts: 13621
  • Posted on: 14/6 10:59
Re: Bad tap water #2
You won't find before and after quoted as a rule because RO filters work on a percentage rejection rate so as it depends on your local supply a before and after reading at the supplier's location will be irrelevant. The only time that can be reliable is if you include a DI stage which will take TDS down to 0, but that's unnecessary for freshwater fish. Typically a new RO membrane with new prefilters will reject 95-98%, depending on composition of water. When it drops below 95% it's time to change the membrane. Prefilters need replacing every 6 months or so as they start to let chlorine through when exhausted and that in turn damages the RO membrane. Mine reduces TDS from 320 ppm to 9 ppm when I've just replaced the filters.

There are only a few manufacturers of RO membranes and most of the branded filter systems are using the same membranes, so the extra price is often about the type of housing and having a "name" on it. Many use the Vyair membranes which is what mine uses, but because it has a simple construction it's very inexpensive to buy.

Personally, rather than run two filters and have to change them both out regularly (HMA and RO) I just use all RO and remineralise.