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The Goldfish Gazette, Issue #115 Are KH and GH Important?
July 30, 2023

Goldfish Care Tips

A Free Monthly Resource For Goldfish Enthusiasts
July 2023
Issue #115

In This Issue
Are KH and GH Important?

For most Goldfish keepers KH and GH are not water parameters that are as closely monitored as pH and nitrates, but if you breed your Goldfish, it may pay to know what your water supply measurements are.

Are KH and GH Important?

The Goldfish breeding season is well advanced in the Northern Hemisphere, but is the growth rate of your juveniles being adversely affected by your water hardness?

I have extremely soft water, and I assumed for many years that soft water would be ideal for raising Goldfish fry in, but one problem with very soft water is, how quickly the pH drops.

Another problem is, Goldfish like hard water which contains high amounts of calcium and magnesium, and this is what the KH and GH tests measure.

Note: KH and GH are measured two ways:
1. Degrees of hardness (dKH, dGH) or
2. Parts per million (ppm).

A degree of hardness = 17.9 ppm, so 3 dKH = 53.7 ppm. Test kits usually show both measurements in a table format.

What is KH (carbonate hardness)?

KH is the measurement of the quantity of carbonates and bicarbonates in water.

The action of the biological filter bacteria when breaking down fish waste is to utilize the alkalinity (carbonate) in the water. This causes the pH to gradually drop (become more acidic).

The higher the KH, the more the buffering capacity of the water. This means that KH helps neutralize acids and prevents your pH from falling too rapidly. With a dKH of 0-1, my water pH starts to drop within days of a water change.

The ideal KH level for Goldfish is between 5-8 dKH.

What is GH (general hardness)?

GH is the measurement of calcium and magnesium ions in the water.

These salts and minerals are essential for healthy biological functions, such as fish muscle and bone development. Goldfish take in these salts and minerals through their gills. If they aren’t present in the water, they must find them in their food.

The ideal GH level for Goldfish is between 7-11 dGH.

In my present location, my tap water dGH is 2.

This may be the reason why I am having difficulty raising fry past the juvenile stage since moving here. The foods I initially feed to fry such as brine shrimp, are full of these essential minerals. Once I start feeding other foods, the juveniles don’t maintain their growth rate.

How to Raise KH and GH levels

The solution is very simple. You don’t need to buy expensive chemicals that need to be administered frequently.

All you need to do is go down to your local garden center and purchase a handful of limestone. (Mine gave it to me for free).

Put the limestone into your filter and it will slowly dissolve releasing calcium and magnesium into the water. The KH and GH levels will rise, as will the pH, and they will be automatically regulated by the pH. The more acidic the water becomes, the faster the limestone will dissolve.

Make sure you get limestone as there are several similar minerals such as dolomite that look the same and have similar chemical makeups but don’t do the same job.

To test the limestone I procured, I put a small handful into a liter (quart) jar of soft acidic water with a pH of around 6.0. Within 4 hours the pH test was quite blue.

You can also use crushed coral or crushed seashells.

The benefit of a higher pH when raising Goldfish was something I came across while researching the affects KH and GH had on the growth of young Goldfish.

I will share the surprising details next month.

Comments? Ideas? Feedback? I'd love to hear from you. Just reply to this e-zine and tell me what you think, or what topics you want to be covered.

Next Month's Topic

PH impact on fry growth

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