Recently, I increased water hardness in my tanks with growing guppies, plants, and molting shrimp. This is because the well water I use went from a GH of 10-17, when I last measured it back around 1991 and 2007, to a too-low GH of 3. The decrease was due to continuous rainfall last few years. I followed the basic ideas in my book (p. 87). Goal was to increase water hardness in my tanks by adding key nutrients Ca, Mg, and K in as easy a manner as possible. This recipe won't increase pH (no carbonate salts) and it avoids loading up tank with sulfates by using commercial products (all the Ca, K, Mg come as sulfate salts).
I prepared (or had on hand) two key stock solutions.
Calcium: One is a CaCl2 (calcium chloride) solution. Mine was a saturated solution in an ancient bottle from a lab giveaway that I have kept for 20 years (photo). All CaCl2 preparations-barring those kept in a lab dessicator or lab oven--usually come with attached water molecules, plus CaCl2 quickly forms a liquid. So you can't really measure out crystals or liquids of CaCl2 accurately and assume you have added so much of the actual Ca. Measuring the effect that a CaCl2 addition has on GH is the best and most accurate way to measure how much Ca you are adding.
I added 5 ml (about one teaspoon) of the CaCl2 liquid (from brown bottle in photograph) to my 20 gal (80 liter tank). Starting GH was 4 and the addition increased it to 8, so the addition increased the GH by 4. This result with a 1:16,000 dilution was very acceptable. Done!
Magnesium: MgSO4 was from Epsom salts I bought at drug store (photo). Crystals came with some added fragrances, but otherwise its mostly MgSO4. Like CaCl2, MgSO4 comes with attached water molecules and gradually absorbs water, so you have to measure its effect on GH.
To prepare stock solution, I added 2 Tablespoons (~36 grams) of the Epsom salts to 2 cups (~500 ml) of tapwater. I had no idea how much this would increase GH, so I tested it by adding 1 ml to a quart of tapwater (~1 liter or 1,000 ml). GH increased from 3 to 5, so I knew that a 1:1,000 dilution would increase GH by 2 solely due to Mg.
Potassium: I purchased KCl from grocery store as a "salt substitute." I added 2 teaspoons (~12 g) to the Mg stock solution I prepared earlier. Fortunately, it did not form a precipitate. Thus, I could add Mg and K at the same time from this Mg/K stock solution.
I decided that my tank would do fine with a:1:16,000 dilution of each of my two stock solutions (Ca and Mg/K) in the tank water. (The main thing was getting enough calcium into the water.) To get a 1:16,000 dilution, I add 5 ml (~1 tsp) of each stock solution to 20 gal (80 liter) of tank water. 80 liters divided by 5 ml = 16,000. For a 10 gal tank, I'll add 2.5 ml of each stock solution, the same 1:16,000 dilution. When I change water I'll just add some of each stock solution. It doesn't have to be that accurate and doubling or tripling the 1:16,000 dilution "dose" that I add should not cause any problems.
In my experience, adding shells (CaCO3) to increase GH hasn't helped that much or worked fast enough. For example, I added 1 tsp of oyster grit to a 1 gal shrimp bowl and a month later GH had not increased above the starting GH of 3. If you use shells, please actually measure the GH in tank water to make sure that they are working.
I prepared (or had on hand) two key stock solutions.
Calcium: One is a CaCl2 (calcium chloride) solution. Mine was a saturated solution in an ancient bottle from a lab giveaway that I have kept for 20 years (photo). All CaCl2 preparations-barring those kept in a lab dessicator or lab oven--usually come with attached water molecules, plus CaCl2 quickly forms a liquid. So you can't really measure out crystals or liquids of CaCl2 accurately and assume you have added so much of the actual Ca. Measuring the effect that a CaCl2 addition has on GH is the best and most accurate way to measure how much Ca you are adding.
I added 5 ml (about one teaspoon) of the CaCl2 liquid (from brown bottle in photograph) to my 20 gal (80 liter tank). Starting GH was 4 and the addition increased it to 8, so the addition increased the GH by 4. This result with a 1:16,000 dilution was very acceptable. Done!
Magnesium: MgSO4 was from Epsom salts I bought at drug store (photo). Crystals came with some added fragrances, but otherwise its mostly MgSO4. Like CaCl2, MgSO4 comes with attached water molecules and gradually absorbs water, so you have to measure its effect on GH.
To prepare stock solution, I added 2 Tablespoons (~36 grams) of the Epsom salts to 2 cups (~500 ml) of tapwater. I had no idea how much this would increase GH, so I tested it by adding 1 ml to a quart of tapwater (~1 liter or 1,000 ml). GH increased from 3 to 5, so I knew that a 1:1,000 dilution would increase GH by 2 solely due to Mg.
Potassium: I purchased KCl from grocery store as a "salt substitute." I added 2 teaspoons (~12 g) to the Mg stock solution I prepared earlier. Fortunately, it did not form a precipitate. Thus, I could add Mg and K at the same time from this Mg/K stock solution.
I decided that my tank would do fine with a:1:16,000 dilution of each of my two stock solutions (Ca and Mg/K) in the tank water. (The main thing was getting enough calcium into the water.) To get a 1:16,000 dilution, I add 5 ml (~1 tsp) of each stock solution to 20 gal (80 liter) of tank water. 80 liters divided by 5 ml = 16,000. For a 10 gal tank, I'll add 2.5 ml of each stock solution, the same 1:16,000 dilution. When I change water I'll just add some of each stock solution. It doesn't have to be that accurate and doubling or tripling the 1:16,000 dilution "dose" that I add should not cause any problems.
In my experience, adding shells (CaCO3) to increase GH hasn't helped that much or worked fast enough. For example, I added 1 tsp of oyster grit to a 1 gal shrimp bowl and a month later GH had not increased above the starting GH of 3. If you use shells, please actually measure the GH in tank water to make sure that they are working.
