SB 104 - The Basics of GH for a Shrimp Tank

To repeat from the previous lesson: If you get nothing else out of this , remember that having stable parameters is much more important than getting the “perfect” pH, KH, or GH, even if your tank is slightly outside the recommended ranges.  DO NOT chase a specific value.  

For GH specifically - If your shrimp are molting fine and not dying, then don't change anything.  If you do have a problem and think it could be caused by GH, then make a small adjustment following recommendations in this lesson, observe or test your tank daily for changes, and respond accordingly.  Please don't hesitate to reach out if you have any issues or questions you would like help with!

Table of Contents

You and your shrimp deserve the best and Shrimply ExplainedTM is here to provide that.  This lesson is part of our Shrimp Basics (SB) Series, which covers important information needed to raise healthy and happy shrimp.    Check out SB101: Are Shrimp Right for You? if you want to start from the beginning.

Please reach out to us via social media or email for any help with your tank, feedback on our content, or just to talk about shrimp!  


Rick and Shrimply

Shrimply Explained™ is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to

What is GH?

GH stands for General Hardness, which is Shrimply’s stage name at his other job.

GH stands for general hardness and is a measure of how many minerals are in the water.  You may also hear it referred to as water hardness or total hardness. Just like KH (carbonate hardness - see Lesson 103 for more info), general hardness is measured in ppm or degrees hardness (dGH) and varies drastically depending on where you live.  It is the main reason someone may refer to their local water as “soft” or “hard” and is partially responsible for the taste of hard water. While GH measures multiple minerals in water, the main two that shrimp keepers focus on are calcium (Ca2+) and magnesium (Mg2+).  Each play an important role in shrimp health.  Calcium is necessary for proper shell formation and molting, while magnesium is necessary for proper absorption of calcium. Magnesium plays the same role in humans, which is why doctors normally recommend taking magnesium when taking calcium supplements.  In addition, every animal uses them for muscle control, including you! We’re really not that different from shrimp, as it turns out.

Technically, GH is a measurement of all the elements in the second column of the periodic table.  Calcium and/or magnesium are commonly found in tap water while the others may only be present in trace amounts, if at all.

How to Prevent Shrimp Molting Problems

Molting problems are an extremely common cause of shrimp death.  They occur when there is an improper balance of minerals and can happen even when GH is within the recommended range for your species.

Wait, what? How is that possible?

Can you imagine how frustrating it would be to seemingly have the perfect parameters but continue to lose shrimp every day?  I know I wouldn’t be in the hobby for long.  Luckily, this frustration is avoided by understanding what GH measurements are really telling you.

As mentioned before, GH measures a variety of minerals – not just calcium and magnesium.  It does not tell you the ratio of minerals present either.  This means you have no idea what makes up the GH in your tap water.  It could be all calcium – or all magnesium – or all strontium (unlikely).  water also varies in composition, so 6 dGH one week might have all the right minerals but 6 dGH the next week is completely different. 

The point is that, while GH is a good indicator that some calcium or magnesium is likely present, it does not guarantee that both are or that they are available in the right ratios needed for successful molting.  It is somewhat similar to porridge bowls in GHoldilocks and the Three Bears.  For those unfamiliar, a quick summary is provided: 

GHoldilocks is a felon who breaks into the house of three bears to steal their breakfast porridge while they are on a walk.  One of the bowls has porridge that is too hot and scalds her mouth, while a second bowl has cold, dribbly porridge that GHoldilocks has too much self-respect to eat—She’s a criminal, not a maniac.  The third bowl happens to be just the right temperature so she can satisfy her hunger and survive long enough to commit more crimes.  Unfortunately, this lulls her into a false sense of security so she falls asleep in her victims’ house and is promptly eaten when the bears get back home. 

The temperature of the porridge is like your ratio of calcium to magnesium.  Both minerals must be balanced or else it will be difficult for your shrimp to survive.  Luckily, the acceptable range for most shrimp species is pretty large--They aren’t as picky as GHoldilocks.   

To repeat myself, GH measurements may be in range, but this does not mean that the ratios of minerals are correct.  So, if you can’t rely on GH to tell whether your water is right for shrimp, then how can you ensure a healthy tank?

There are a few ways to ensure your water has suitable mineral content but the most accurate and reliable is to use products called remineralizers.  If fact, they are so effective that nearly every shrimp breeder in the world uses some type of remineralizer (and most use RO/DI water but we’ll get to that in a bit).  These products are quite easy to use because you simply add them during a water change until you reach the desired GH (Be sure to add the remineralizer into the new water being added to the tank and NOT the tank water itself.  These products should never be added directly to your tank except in very small amounts because they cause immediate changes that stress your shrimp).

Please note that some remineralizers only increase GH while others increase both GH and KH so it is important know which one you need and pay attention to what you buy. 

How to Use a Remineralizer

The most common way to use remineralizers is to combine them with purified water commonly known as RO/DI (Reverse Osmosis/Distilled or Deionized) water.  These acronyms refer to the ways in which the water is purified but each method produces water that has 0 GH, 0 KH, and slightly below 7 pH.  With RO/DI water, simply add remineralizer until you reach the desired GH and KH (or more commonly total dissolved solids), then add the remineralized water slowly into your tank.  Repeat for every water change. (RO/DI water is used by many shrimp keepers because it allows complete control of your tank water, whereas you never know what contaminants may be in tap water.) The process becomes a little more complicated with tap water because it rarely has 0 GH and KH.  You must know what parameters the tap water has already and what parameters your shrimp thrive in.  Let’s use a Neocaridina (neo) tank that has been losing shrimp to molting issues as an example, along with tap water that is 8 dGH (~160 ppm – Remember that 1 dGH or dKH is approximately 20 ppm) and 8 dKH (~160 ppm). The generally recommended neo range is 6-14 GH and 0-10 KH. We can assume that part of the 8 GH is made up of calcium or magnesium so it is not necessary to increase GH by a full 6 dGH.  Instead, aiming for +3-4 GH is likely to provide enough of the missing minerals to solve any molting issues.  That would put the tank GH at 11-12 dGH, which is still within acceptable neo range.  Since we can’t change out all the water at once, do  10-20% water changes with the 11-12 dGH remineralized tap water over a few days until the tank reaches 11-12 GH.  Watch the tank for molts for to verify the problem is fixed. There is one more issue that needs to be addressed.  During that whole process, what is happening to KH? If you are not familiar with KH, please read our previous lesson covering The Basics of pH and KH in Your Tank. Well, remineralizers have different ratios of GH to KH – One may add 1 dKH for every 1 dGH while a second only affects GH.  Others may add entirely different ratios than those mentioned so it is important to read the label.  For our example, we want a remineralizer that does not increase KH above 10 dKH (a +2 dKH change) while increasing GH by 3 or 4.  4/2 = 2 so the ratio of GH:KH in the remineralizer used should be less than that. To be clear, remineralizers are only needed when using RO/DI water or when experiencing molting problems.  There are also other methods of raising or lowering GH that we’ll cover later.  That being said, while remineralizers might seem complicated initially, they quickly become routine and are the best way to make precise changes to GH.

The GH Creep

(Another common problem experienced by shrimp keepers, explained in story format)

You wake up with a sense of dread.  As you groggily get up out of bed, your bleary eyes are suddenly blinded by a light turning on in the corner of your room and you’re forced to flinch away.  The source of light is coming from your aquarium lights as the broken timer turns them on 2 hours early.

“Damn it – Are you kidding me?  What the – You’re a timer!  You’re supposed to clock- I mean, time things!” You exclaim, attempting to vent your frustration on an inanimate object with what little pre-coffee brain power is available.

The grogginess doesn’t last long though, after seeing what’s lying on the tank substrate.  A shrimp twitching with the white ring of death – the sign of a failed molt. 

Being a good shrimp keeper, you leap into action and pull out the test strips, dip one in the tank, pace around the room while waiting for the colors to develop, then find a GH reading of 400 ppm (~20 dGH).

“Wha- My tap water is only 200. How?” You ask to an empty room. But the room does not disclose its knowledge, leaving you confused and depressed.

Suddenly, another bright light appears in the corner! 

“What the-“

Out of the whiteness swims Shrimply, hovering above the carpet and covered with a golden glow.    

“I am here to take this one to the place where good shrimp go,” States Shrimply, in a voice deep enough to rattle your very bones.  Though grasping for words, you find none, allowing silence to layer the room like sediment crushed by the weight of the ocean.

Shrimply glides to the tank with a gentle whoosh that disturbs the stratified silence, dipping his claw in to scoop up the poor shrimp then heading back toward the light.  Before slipping through, he leaves you with these fateful words.

“It was the GH creep that got her.  When water evaporates from your tank, it leaves behind minerals and they concentrate in the tank.  By always topping off with tap water when evaporation occurs, you add extra minerals and allow more to build up over time.  The GH slowly reaches up, like a stealthy stranger in the night, eventually stealing your shrimp away--but it’s possible that I can save this little one.  And you can protect the rest in your tank by doing water changes with RO/DI water to bring down GH.  Goodbye.” 

And with a flash, Shrimply disappears.

(Not to brag, but this story is actually what earned Shrimply Explained the award for the Weirdest Shrimp Guide on the internet from a very prestigious institution.)

The moral of the story is to watch out for a build-up of minerals in your tank if you are just topping off with tap water and to measure your water hardness every so often, even if you don’t think you need to. 

How to Test GH

GH can be tested with either test strips or liquid test kits.  As mentioned in the previous lesson, test strips are cheap and fast but can be inaccurate while liquid test kits provide greater accuracy and reliability at a higher cost.  If you already have test strips that measure GH then you are welcome to use them but we highly recommend the liquid test kits from API instead.  

Controlling GH

How to Lower GH in Your Aquarium

Please note that all options to lower GH also lower KH

1. Use Softer Water for Water Changes

The easiest and most controlled option to lower GH is to add softer water to your tank during water changes. Please note that softer water does not mean water from a water softener. A water softener simply replaces calcium and magnesium with sodium, which is not great for shrimp.

If your tap water happens to be softer than your tank water, then doing a water change is the cheapest option to lower GH – but most people who want to lower GH are doing so because their tap water is too hard.  When soft tap water is not available, then RO/DI/spring water can be purchased from your local grocery or fish store.  You can also buy a reverse osmosis (RO) or distilling system for less than $100 for the convenience of not needing to lug gallons of water from the store.  

RO systems use pressure to push water through 3-5 filters with the end product being close to pure water.  These systems can produce large volumes of water throughout the day so are excellent when caring for multiple large tanks. Some remove chlorine and chloramines while others do not, so it is important to be aware of that when considering which to purchase.  Be aware that, for every 1 gallon of water produced, up to 4 gallons gets wasted so they are not very efficient.  Typical prices are $60-300.

Distilling systems, on the other hand, are extremely efficient, producing almost exactly the same amount of water put in.  They also produce the purest possible water through an evaporation process that removes all minerals/contaminants.  The downsides are that the process takes up to 5 hours to produce a gallon of water for home systems and is energy intensive.  Overall, distillers are an excellent option when less than 20 gallons of ultra-pure water is needed per week.  Typical prices are around $100-300.

Our recommended RO and distilling systems are provided below:

2. Peat Moss

Peat moss contains compounds that bind minerals to remove them from the water, thereby lowering GH.  This is a biochemical process known as chelation, if you wish to dig deeper into this subject on your own.  Lowering GH with peat moss is not an exact science due to differences between batches so water parameters should be carefully monitored during initial use.  It also can only hold so many minerals so is not sufficient for extremely hard water.  Lastly, peat releases tannins which are beneficial in fighting disease but also give water a brown tint. 

How to Raise GH in Your Aquarium

1. Tap water

If your tap water has higher GH, then simply doing a water change will increase GH in your tank.  This is the cheapest way of increasing mineral content but is area and time dependent.  Water from a single sink can vary significantly depending on the cycles of the water treatment facilities in your area so it is always important to measure parameters before each water change.   Also, always be aware of GH creep when using tap water during water changes. 

2. Remineralizers

As discussed previously, remineralizers provide the greatest amount of control over GH, especially when used in combination with RO/DI/spring water.  They can be somewhat expensive ($10-20) and can cause problems if used improperly (i.e. dumped directly in a tank), but the consistency and assurance against molting problems--when used correctly--makes them extremely useful tools for shrimp keepers.

Shrimply Explained™ recommends getting a shrimp-specific remineralizer because those ensure the right ratio of minerals, whereas ones not designed for shrimp may rely on unnecessary or even harmful minerals.  Also, be aware of how your remineralizer affects KH as some species of shrimp want higher KH while others do best in low-KH conditions. 

A Warning About Homemade Remineralizers

We do not recommend attempting to make homemade remineralizers with Epsom salt, baking soda, or other common household ingredients. It is very difficult to get the right ratio of minerals without a strong understanding of the science behind it. Please use with caution.

SaltyShrimp GH/KH+ Remineralizer 100g

This remineralizer is recommended for all shrimp except Caridina (crystal, Taiwan bee, some tiger shrimp, and any hybrids).  It has a 2:1 GH:KH ratio.  A 100g container lasts approximately 2 years for a 20 gallon tank when refilled exclusively with RO/DI water.  For larger setups or more tanks, 200g or 750g of Salty Shrimp GH/KH+ may be a better investment.

SaltyShrimp GH+ Remineralizer 110g

This remineralizer is recommended for all Caridina species, including crystal, Taiwan bee, some tiger shrimp, and any hybrids.  It is also recommended whenever you want to change GH without changing KH.  A 110g container lasts approximately 2 years for a 20 gallon tank when refilled exclusively with RO/DI water.  For larger setups or more tanks, the 230g or 850g containers of Salty Shrimp GH/KH+ may be a better investment.

3. Crushed Coral/Aragonite or Wonder Shells

These products are made of calcium carbonate that slowly leaches into your water over time to increase GH, KH, and pH. They are excellent sources of calcium, but they do not contain any magnesium so you may experience molting problems if your water does not already have magnesium. As such, always start with a small amount, measure the effects over a few days, then adjust as necessary. We recommend putting crushed coral or aragonite into a bag so it is easy to remove from the tank as needed.

A few Wonder Shells cost between $10-30 while a bag of aragonite or crushed coral cost between $20-30 typically. This makes these products among the most expensive options for raising GH but they last for a few years so can be a worthwhile investment. 



As you now know, GH is one of the most important parameters due to the problems that mineral imbalances cause.  Understanding how to measure and control GH eliminates many of these issues, hopefully allowing you to enjoy shrimp keeping significantly more.  Armed with this knowledge, along with information from the previous lesson on pH and KH, you are now ready to start setting up your tank!  The next lesson on tank setup is being worked on now.  Please subscribe to our email list to be notified when it gets published and continue your Shrimp School education!

If you still have questions, please reach out on social media or send us an email at  We are here to help however we can and love meeting new members of the community.

Oh, and have a great day :)

The Chitin Chronicles Newsletter


Copyright © 2024 Shrimply Explained.  All Rights Reserved.
Get your shrimp fix with Shrimply Explained on social media!
Copyright © 2021 Shrimply Explained.  All Rights Reserved.
linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram