Help With Water Hardness!

When you say too high what do you mean? It really depends on what fish you're planning to have!

Ph and hardness are quite complicated to change, so an easier option may be to keep fish that like your water conditions. 

If you're not happy with that option the best option would be using RO water

RO: Reverse Osmosis: a method of making pure H2O with NO impurities.  Needed for marine, where you then add the correct amount of salt to ensure the salinity is exactly what you want.  Could also be used for tropical, but expensive compared to tap water, and you'd find yourself adding salts of some kind or other to maintain the buffering capacity (hard water will retain pH very well: large "buffering" capacity).

I have v. hard water: it goes with a high pH (my tank's pH 8.5 or thereabouts).
One way to check is to get the water quality report for your area (affinity water let you search by postcode).
Likely to be more accurate than test strips (though if you have limestone gravel in your tank ...).

I'm setting up a new tank at present: this site has great information on pH tolerances (and sizes and tank loading), from which I'm selecting Dwarf Rainbows, X-Ray tetras to go with my current small shoal of harlequins that I've moved from my old tank.

According to thinkfish site, both knife fish and silver sharks would be ok with hard water/pH 8.5, but watch out ... they grow massive (30cm+): thinkfish are recommending a tank of at least 1.2m for the knifes, 1.6m for the silver sharks.  I'm steering clear of these as they'd get far too big for my 120l tank.

The problem with using pH down type products is that the pH can fluctuate, which is not good for fish.

Let me just run through a few definitions.

pH measures the amount of hydrogen ions in the water. As acids release hydrogen ions, it is a measure of acidity. And since it is an upside down measure the more acid, the lower the pH
GH is a measure of divalent metal ions. In reality our water supplies contain mostly calcium and magnesium as divalent metal ions; others are there only in trace amounts. It is usually expressed just as calcium.
KH is a measure of the buffering capacity of water. The main water chemical that does this is carbonate, which is why buffering capacity is referred to as carbonate hardness. Water companies call it alkalinity if you come across that term on their website.

Carbonate (KH) reacts with acids and neutralises them. If the KH is high, it has to react with a lot of acid before it is used up. The products that lower pH do so by adding acids and with a high KH the pH drops for a while, then the carbonate reacts and the pH bounces back up.

The other problem is a fourth measure, TDS ie total dissolved solids. If you add something to the tank eg pH down, there are more things dissolved so the TDS goes up, the opposite of what you want.



As the others have said, the only realistic way to lower pH and hardness is by diluting your tap water with pure water - either de-ionised or reverse osmosis. But you must find the ratio of the two that gives the result you want and use that exact ratio at every water change. Using 100% tap water if you run out of DI or RO will change the hardness and pH and harm the fish. Now is the time to experiment to find the ratio and replace all the current water with the mixed water, before you get fish.

The other alternative is to stick to fish that like hard alkaline water.

Maidenhead Aquatics sell RO water but as mine dont deliver I buy di-ionised water from my local hardware store, they order it in for me and deliver it too. Its the water you'd use to top up a car battery basically. I followed Sue's instructions and gradually replaced 50% tap water with di-ionised water over a period of a couple of months

Make sure its not been opened or contaminated by petrol or oil though if your mates going to supply it from a garage would be my only word of caution

Thank you, experimenting love it  .

I will be careful of contamination, it will just be easier and cheaper through him, as trade discount.

Now to research fish and decide wether to have fun with experimenting or if there are species I am happy to have with the current hardness.

Any suggestions as a starting point?

Thank you again for your help.

I have got a good idea of what to stock with now from the fish profiles on here. I actually found quite a lot that I liked that are hard water compatible, it also help that I have a 200 litre tank, so was less restricted on size. I just need to get a more accurate hardness reading to make sure they are all suitable.

Just need to find a decent LFS, as the ones local I've used before don't seem that great now after reading a few of the fish profiles. I know most stock parrot fish and the two I used regularly both sold me silver sharks, which I have now discovered are too big for my tank, yet I was sold several and told my tank had ample room.