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Super hard water, thinking ahead for 4ft tank

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bbtom10

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14 Oct 2024
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Hi, I am about to upgrade from a 100cm 120L to a 4ft 288L tank and I’m concerned my water is too hard.

I have 3 nano tanks and the aforementioned 120L, and they all report high Ph (c.8) and high Kh (c.18) but the most worrying is my general hardness, measured with a water monitor, is between 500 and 900ppm. All tanks have plants and fish and seem to be healthy enough, but in the new tank I’ll be including CO2 as well and a lot more hard scape (slate and wood).

So, should I be storing rainwater, or installing a water softener to my tap in order to maximise plant health and fish health, or just accept I have very hard water and as long as nothing dies accept what I get?

Appreciate thoughts while I keep playing in my cardboard dojo waiting for tank delivery!

Tom
 
bbtom10 said:
installing a water softener
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If you’re thinking ion exchange softener that uses salt, then no, as it’s bad for the fish. Calcium and magnesium is replaced with sodium. Either live with the hard water, use rainwater as you suggest or use RO which you can remineralise with some of your tap water.

Many people on this forum have rock hard water, e.g. in London and Cambridge and grow plants successfully.
 
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bbtom10 said:
Hi, I am about to upgrade from a 100cm 120L to a 4ft 288L tank and I’m concerned my water is too hard.

I have 3 nano tanks and the aforementioned 120L, and they all report high Ph (c.8) and high Kh (c.18) but the most worrying is my general hardness, measured with a water monitor, is between 500 and 900ppm. All tanks have plants and fish and seem to be healthy enough, but in the new tank I’ll be including CO2 as well and a lot more hard scape (slate and wood).

So, should I be storing rainwater, or installing a water softener to my tap in order to maximise plant health and fish health, or just accept I have very hard water and as long as nothing dies accept what I get?

Appreciate thoughts while I keep playing in my cardboard dojo waiting for tank delivery!

Tom
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Hello @bbtom10 Wellcome to UKAPS! 🙂

To make a meaningful dent in your high water hardness you will have to use at least 50% Rain or RO water - do not use water softened (ion exchanged) with NaCl (Sodium chloride pellets - table salt essentially). To exchange your level of Calcium (and Mg) you will end up with about 200 mg/l of Sodium in your tank water, which would be terrible. You can however use Potassium Chloride (KCl pellets) instead - way more expensive, but perfectly fine, except that you will end up with a lot of Potassium in your tank. In our house hold we use water softened with KCl, but for my tanks I use RO water regardless. You can definitely grow plants from the easy category in very hard water. Your choice of livestock might be a bit tricky though. I would stay clear of fish that really prefer softer water - yes, a lot of softwater fish bred in capatitivty are fairly well adapted, but its more about tolerance rather than what they prefer and thrive in - and you want your livestock to be happy 🙂

Cheers,
Michael
 
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Thanks both. I was indeed already put off by the thought of converting hardness to salt. I was thinking either some sort of magnetic filter, or an RO filter. As stated, my current tank is fine with CPDs, black emperor tetra, black neons and panda Corys. Most are 2 years old now and still seem happy. I’ve always struggled with getting plants to thrive. Crypts and epiphytes seem ok, limnophelia and val are growing fine, Java ferns tend to go brown within a few months and carpeting plants die in a burst of hair algae.

I do tend to struggle with green hair algae after a while in all my tanks - not sure why this is. Lighting tends to be on for 8hrs max.

My substrate is MD fish tank method… some topsoil (will be pond compost next time), nutribase, some gravel and sand cap. Some plant nutrients in the form of nutristicks.

My new tank will have all the healthy plants transplanted over, along with a load more crypts and epiphytes and a few stems. Hoping the CO2 and some more ferts are enough to really get the plants going. In my head I’m doing a first attempt at a competition style layout, but we will see. Planning to do a journal as well. I guess at some point I should do an intro post!

Anyway, your thoughts are appreciated.

Tom
 
Maf 2500 said:
Rainwater has the benefit of being free (once you have storage installed). Also if you happen to live near a Spotless Water location that would be a cost effective alternative to installing your own RO system.
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Spotless water site not far from me… might be worth 50%tap, 50% spotless. Thanks, never heard of them!
 
bbtom10 said:
Spotless water site not far from me… might be worth 50%tap, 50% spotless. Thanks, never heard of them!
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I would go 60% RO/spotless and 40% tap and perhaps short a bit on the WC frequency / amount, but since you're running a CO2 tank - with a high metabolic rate - that may not be an ideal choice. Either way, make sure you don't burn out on the maintenance. Hauling 70 - 85 liters of water for your 288 tank (assuming a 50% WC with 50% RO / 50% Tap - 60% RO / 40% Tap) is no fun after a couple of times.

Cheers,
Michael
 
MichaelJ said:
I would go 60% RO/spotless and 40% tap and perhaps short a bit on the WC frequency / amount, but since you're running a CO2 tank - with a high metabolic rate - that may not be an ideal choice. Either way, make sure you don't burn out on the maintenance. Hauling 70 - 85 liters of water for your 288 tank (assuming a 50% WC with 50% RO / 50% Tap - 60% RO / 40% Tap) is no fun after a couple of times.

Cheers,
Michael
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This is what I’m thinking, thanks.

I think the other problem I have, and which is probably why I get algae, is less and less frequent water changes. I’ll be doing 50% weekly while the tank beds in (using old filters so fish-in cycling) so that should mean maybe 100L of RO a week will be ok, and as my water change amount reduces I can use more rainwater as well. I am conscious of mineral concentration if I top up with tap water, but as long as I keep track then shouldn’t be a problem.

My fish are happy, my challenge now is happy plants!

What does “high metabolic rate” mean?
 
The right mix of plants and fish will thrive in hard water.

Don't expect to keep wild Discus or Apistos and fish from those kinds of habitats though.

And plants like Toninas, Eriocaulons and Syngonanthus are definitely out of bounds, lol.

Most 'non sensitive' fish will be ok once acclimatised.

But in my experience, keeping plants healthy and growing well in proper hard water is always a much bigger challenge than soft water.

RO units are a good option for a much larger variety of plants and fish but i am not a big fan because it is not very sustainable and wastes a lot of water.

As people have said, Vals love hard water so a junge style setup with vals reaching and covering a part of the surface might work well.

Elodeas love hard water but nobody seems to want those in any scapes these days!

Ludwigias can generally get used to it, but undiagnosed deficiency issues might crop up in hard water.

I have always struggled with rotalas in hard water, but some people grow it successfully.
 
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