Making your own RO for freshwater

[ZoddyZod]

Hello,

I'm potentially looking to keep a stingray. For that reason I'll need to be buying RO water and having calculated it will cost me ~£20 to buy RO from the LFS, I'm looking to invest in my own RO system.

There seem to be plenty of options for the actual equipment, but I haven't seen a clear guide on how to remineralize or what products/chemicals are needed for that.

Does anyone on here produce their own RO for a freshwater aquarium and could they please offer some advice on what's needed?

 

[Colin_T]

Reverse Osmosis (R/O) units come in a range of types and some are better than others. The good models have a 1:1 ratio of waste water, meaning they produce 1 litre of waste water for 1 litre of R/O water. The not so good brands will have a 1:2 or 1:3 or even 1:4 ratio, where they produce 1 litre of R/O water to 2, 3 or 4 litres of waste water. The waste water contains the minerals that are removed from the water.

If you live in an area with water restrictions, you might find it is expensive to make R/O water, so try to find a good unit that has a 1/1 ratio.

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What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).

If you have soft water coming out of your tap, you might not need to use R/O water.

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What are the tank dimensions (length x width x height)?
Sting rays need a big tank with clean water. If there is ammonia, nitrite or nitrate in the water, they get pink skin on their belly, so watch for this and test the water regularly.

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You can use a Rift Lake conditioner for African Rift Lake cichlids to add minerals to the water. However, if you are keeping South American stingrays from the Amazon, they come from soft water with a low mineral content and don't need many minerals in the water.

 

[ZoddyZod]

I have no restrictions on water costs/usage - I pay a flat rate.

The water I have is around 8 pH, and is known to be very hard - but I don't have the specific KH & GH values.

Tank is 6x2x2 and I'm limiting myself to a single ray. I've had several conversations with a local breeder on what is suitable (and hence my questions on RO).

So, if I can produce my own RO, specifically what remineralization products can I buy and is there some sort of guide for reproducing the levels that specific rays would live in in the wild?

 

[Colin_T]

Look for a Rift Lake water conditioner at your local pet shop. I don't know what's available in your country so can't advise on specific brands.

The packet of mineral salts will give you a dose rate to use and should tell you how hard the water will get when you add that dose rate.

Depending on what species of ray you keep will determine what the GH and pH should be.

 

[seangee]

Just to add - don't be tempted to get an RO unit with an extra stage to "add back" minerals at the end. These produce incredibly variable results Do as Colin suggests and add mineral salts using a dosage to achieve the correct levels for your selected species.

FWIW I use a mixture formulated for shrimp for my tank that need moderately soft water. The brand is Salty Shrimp. It may be worth checking what your LFS uses when they sell re-mineralised RO because you will know you can always get it. Mine uses a Marin product but I am happy with the results with the Salty Shrimp GH/KH+. In my case I add one teaspoon to 10 litres of RO to get a GH of 6dGH and KH of 3dKH.

Also FWIW do you know your water provider's schedule for switching to metered water? About a week after I installed my RO unit I got a letter to tell me our meters were being installed the following week. I don't believe I had any prior notice.

 

[ZoddyZod]

thanks for the advice. Having thought about this some more I'm ditching the stingray idea. I don't really want to invest either the time or money into RO. Given my hard water I'm going to switch to CA cichlids instead and keep using tap.

 

[ZoddyZod]

and now, after having watched a few youtube videos that show how easy it is to use RO equipment, I'm interested again! I saw some Geophagus winemilleri yesterday and that certainly helped.

I've read that using tap water as a buffer is an option. If I'm looking to keep amazonian fish what hardness levels should I be looking to recreate? Are the levels stated above (6dGH and KH of 3dKH) about right?

I'll obviously need to play with mixing some tap and RO until I get the right balance, but just asking what levels I should be looking to achieve first.

 

[seangee]

I've read that using tap water as a buffer is an option. If I'm looking to keep amazonian fish what hardness levels should I be looking to recreate? Are the levels stated above (6dGH and KH of 3dKH) about right?

That will work for amazon fish - but what species are you looking at?
For my South American tank (tetras, corys, pencilfish and a bristlenose) I use straight RO. That's obviously really easy. In another tank I have celestial pearl danios and red cherry shrimp and I keep that one at 6 dGH, mostly because of the shrimp.

I used to mix RO with tap water to get 6 dGH in the SA tank and 12 in the shrimp tank. An added complication is that my tap water has nitrates at 50ppm so I had to filter the tap water to remove nitrates and then mix it with bought RO water. It turned out much easier just to bite the bullet and do my own RO. At the time the harder water was to try to balance how much water I had to cart from the LFS every week.

FWIW my supplier is Southern and the water comes out of the Crowthorne reservoir. May be worth checking your tap water for nitrates as I guess you also use ground water and (at the closest point) Surrey is only a couple of miles from me.

 

[ZoddyZod]

Straight RO? I thought that was a no-no as you need at least some trace elements present?

Haven't set on the exact species, but broadly it will be SA cichlids and accompanying dithers from the same region.

 

[ZoddyZod]

I'm in Bagshot, just down The road from Crowthorne. Haven't a tested for nitrates in years though.

 

[seangee]

Straight RO? I thought that was a no-no as you need at least some trace elements present?

Haven't set on the exact species, but broadly it will be SA cichlids and accompanying dithers from the same region.

I always thought that too. When I decided to abandon tap water altogether I asked on here what to target for GH for my species and several people suggested leaving it at 0. I have been using it for over 6 months and the fish are thriving. Surprisingly the MTS are also fine. Best to check specifically for whatever species you plan, but interestingly the breeding advice for all my species is to breed and raise fry in RO water. I haven't gone RODI so its not quite pure but what's left is negligible - typically 9-15 ppm on the TDS. I don't bother with TDS but installed an in-line meter so I know when my membrane needs replacing.

FWIW I understand Maidenhead Aquatics in Sunningdale will have a dedicated soft water section once the revamp is complete.