• You are viewing the forum as a Guest, please login (you can use your Facebook, Twitter, Google or Microsoft account to login) or register using this link: Log in or Sign Up

RO vs Tap

P

Pixies

New Member
Joined
25 Aug 2024
Messages
7
Location
Edinburgh
Hi. A bit of background first:
I started (like many, I guess) as wanting to keep an aquarium for fish. I wasn't particularly interested in plants to start with, although I knew I didn't want plastic decorations. This was 15 years ago. Now over the years the plants have increased.

I always had trouble with algae (mainly green hair). I'm in Edinburgh so the water is very soft, it's also quite high in Phosphate. My son was dabbling in a marine reef tank so was getting RODI water from the local shop. After some very limited reading and advice, I started using RO water myself, with JBL Aquadur - and things improved greatly. For years I carried on like this and after a few tank upgrades I've still been using it. However, at the start of this year the green hair came back with a vengeance and I couldn't get it out of the Java moss and driftwood. I eventually relented and completely stripped out everything and started a fresh tank. I'm wanting to have more plants now and after finally researching online (here mainly) realise that this will be my main defence against algae. Also, I see that phosphate isn't the great evil with a planted tank.

I'm staying lo-tech and the substrate is inert. Perhaps I would have used something else if I had committed to a planted tank before redoing it. It's a Superfish Home 85 litre.

Anyway - to my question, eventually: what water should I use?

My tap water (after 4 hour degassing) is: kH:1, gH:2.5, pH:7, phos:4.8ppm, TDS:40
As an example, my tank water before my weekly 50% water change is: nitrate: 10ppm, kH:5, gH:7, pH:7.5, phos:0.05ppm, TDS:200

Is it worth considering going back to using tap water? It is very soft and lacking in TDS. Perhaps using a mix of my usual RO/Aquadur with some tap? Or perhaps even just using tap with Aquadur (or similar)?

Cheers
 
Interesting. You can see how the plants are taking up the phosphate as your tank water is lower than your tap (assuming measurements are accurate and reliable). Do you fertilise, adding P and K? No need for P.

If I had tap water like yours I’d not bother with RO.
 
Last edited:
hypnogogia said:
Interesting. You can see how the plants are taking up the phosphate as your tank water is lower that your tap (assuming measurements are accurate and reliable). Do you fertilise, adding P and K? No need for P.

If I had tap water like yours I’d not bother with RO.
Click to expand...
Sorry if I wasn't clear. I'm not using tap water in the tank currently. The pre-water-change figures above are for my usual RO + Aquadur.
 
Are you adding fertiliser? I wonder if it's just your tap is so light on everything, that remineralising is adding some nutrients your plants need so it seems like it's better than tap, where as tap+fertiliser would work the same.
 
Thanks everyone for responding and sorry if I haven't made myself clear.
Also - I didn't want to get too much into fertilization, as this isn't the forum, but all things are related anyway.
tam said:
Are you adding fertiliser? I wonder if it's just your tap is so light on everything, that remineralising is adding some nutrients your plants need so it seems like it's better than tap, where as tap+fertiliser would work the same.
Click to expand...
I am using RO water with Aquadur, which adds just kH and gH - no macros or micros. I have been relying on nitrate from fish waste and using Maidenhead's Microbe-Lift Plants Green Fertiliser which is micro-only, along with their Microbe-Lift Bio CO2 Liquid. This was all based on my false aversion to phosphates.

So - is it worth using my tap water to get the additional phosphate? I'll need to add the kH and gH too, as it's lacking from the tap water.
 
What livestock do you have? Your tap water is good and you won’t need to increase GH or KH unless you have shrimp and/or snails, or livebearers who seem to enjoy harder water as well. If you do end up using your tap water, you just need to fertilise micros and potassium and nitrogen.
 
hypnogogia said:
What livestock do you have? Your tap water is good and you won’t need to increase GH or KH unless you have shrimp and/or snails, or livebearers who seem to enjoy harder water as well. If you do end up using your tap water, you just need to fertilise micros and potassium and nitrogen.
Click to expand...
I do have a couple of nertite snails plus neocardinia and amano shrimp.

Aside from the molluscs/crustaceans, isn't a kH of 1 just a bit too low to stabilize the pH?
 
Your caridinia would be ok in low kh and GH of 4-6, but the nerites need harder alkaline water as their shells will otherwise erode. Aim for something like 8 for your kh and GH.
 
hypnogogia said:
Does Aquadur contain phosphate?
Click to expand...
No, it contains ~ Calcium chloride, calcium sulfate, magnesium chloride, sodium bicarbonate, potassium bicarbonate. In no particular order.
Pixies said:
Aside from the molluscs/crustaceans, isn't a kH of 1 just a bit too low to stabilize the pH?
Click to expand...
The kh and gh you have from the tap is perfect for the fish, and plants.
Far better imo than RO water with an added tds of 200. BTW, ditch the Aquadur, you really don't need it.
Water via the tap, add a bit of magnesium. Job done 😀
 
You must log in or register to reply here.
Back
Top