Hard Water Concerns

[Slider]

An excellent forum - plenty of helpful information and people.

I am a newbie looking to set up a 75g planted tank in a hard water area. I've had a trail through the threads on this forum but haven't found much on hard water chemistry, so apologies if this had been aired before.

Out of my tap the measured KH is 130mg/L, GH is 220 mg/L and pH is 7.0/7.5. (Curiously, if the water is left to stand in an inert container (glass dish) over 2 days, the pH rises to 8.0/8.5 ??)

I have been told that very hard water is not the best environment for good healthy plant growth and that water of this kind will not so readily absorb CO2 and other treatments such as fertilizers. I have looked at mixing RO water with my tap water to reduce the hardness but I'm not sure if this is really necessary and want to avoid this dependency if possible.

I would welcome any comments on whether high values of water hardness/pH significantly effect plant growth and the efficiency of treatments, and if this is the case what is the best way to overcome the problem.

TIA.

 

[George Farmer]

Welcome to TFF!

The majority of plants will do fine in hard water, with some actually dying off in soft water. As a general rule of thumb then plants that orginate in soft water will do fine in harder water, plants that come from hardwater areas will die off in soft water i.e. some Vallisnera sp.

Personally I'd stick with tap water unless you're attempting to grow particularly demanding plants and intend keeping fragile softwater fish.

In my experience extra CO2 is not required in harder water.

There is an article in the latest (released today) Practical Fishkeeping magazine that covers this subject to a degree.

 

[Liam]

I have very hard water with a similar ph to yours and most plants do fine in it. Some won’t tolerate it. The difference in ph when water is left out is due to the Co2 gassing off, so there is less carbonic acid in the water and a higher ph. I think if you have higher light Co2 in hard water is useful; the plants don’t get the not so attractive calcium deposits of the leaves and grow faster in my experience. 75 gallons is quite a lot and doing ro water makes water changes more of a hassle.

 

[Slider]

Thanks for your replies and your welcome.

If the CO2 is going to naturally 'gas off', presumably this will occur in the tank as well. Should I expect to be running the tank at a similar pH of around 8.0 once it is set up? or will the pH value tend to reduce once the aquarium is mature?