Necessary cookies keep the site working. With your permission we also load analytics (Google Analytics, Microsoft Clarity) and advertising (Google AdSense). Declining does not limit the guides or your account.
One of the most common mistakes when preparing water for a shrimp aquarium is assuming that water coming out of an RO unit is ready to use. Another is believing that reaching a target number on a TDS pen means every water parameter is correct.
In a healthy shrimp aquarium, what matters is not just how many minerals the water contains, but which minerals it contains and how stable those conditions remain.
For Crystal Red, Taiwan Bee and other sensitive Caridina lines in particular, water preparation is a fundamental part of successful husbandry. Neocaridina shrimp may require different mineral and alkalinity targets.
So what exactly is RO water? How do GH+ and GH/KH+ differ? What should the TDS be? How do you prepare minerals in a five-litre container?
This guide takes water preparation from theory into practice, explaining step by step what measuring devices tell us and how to make the water we prepare safe for shrimp.
What Is RO Water?
RO stands for Reverse Osmosis.
In reverse osmosis systems, water passes through a semi-permeable membrane, separating it from a substantial proportion of its dissolved substances.
This process can reduce the amounts of many ions and various contaminants in the source water.
RO systems do not remove every substance completely, however. The result depends on the membrane, feed water, pressure and maintenance of the system.
For aquarium use, the main advantage of an RO unit is that it provides low-mineral starting water over which we have greater control.
We can then rebuild its hardness and mineral composition to suit the shrimp we keep.
Why Should RO Water Not Be Used Directly?
RO water generally contains very little calcium, magnesium and other minerals.
Shrimp need a suitable mineral balance for normal physiological functions, growth and exoskeleton development.
Adding untreated RO water to a shrimp aquarium is therefore not an appropriate husbandry approach, particularly over the long term.
The aim is not to keep the water as pure as possible, but to remineralise it in a controlled way.
Why Use RO Water in a Shrimp Aquarium?
Not every aquarium needs an RO unit.
In some areas, tap water may already have suitable properties for keeping certain shrimp species.
If tap water is very hard or changes throughout the year, however, maintaining consistent conditions can become difficult.
RO water is particularly useful when:
Tap-water GH and KH exceed the intended range.
The mineral content of the water supply changes seasonally.
Sensitive bee-type Caridina colonies are being raised.
Low-KH aquariums with active substrates are being established.
Similar water conditions are needed across several breeding tanks.
Mineral levels and conductivity are monitored regularly.
Imagine a Neocaridina aquarium and a Taiwan Bee breeding tank in the same room.
We can use the same RO water as a starting point for both. That does not mean adding the same mineral mixture for each aquarium.
The preparation method should be determined by the animals' needs.
What Are GH, KH, TDS and Conductivity?
Four terms come up frequently when preparing water for shrimp:
GH, KH, TDS and electrical conductivity.
They are related, but they do not measure the same thing.
GH: General Hardness
GH describes the general hardness of water.
Aquarium tests primarily assess the contribution of calcium and magnesium ions to hardness.
GH is usually expressed in °dGH.
It is an important parameter for mineral balance and moulting in shrimp.
A GH test does not, however, tell you how much calcium and magnesium are present individually.
Two water samples with the same GH can have different mineral compositions.
KH: Carbonate Hardness and Alkalinity
In the aquarium hobby, KH is used to assess the water's ability to buffer acids.
In freshwater aquariums, much of this capacity commonly comes from the bicarbonate and carbonate system.
KH can affect how pH responds to changes.
KH and pH are not the same thing, however.
Low KH may be a target in Caridina aquariums, particularly those using active substrates.
Neocaridina aquariums may use a different alkalinity approach.
TDS: Total Dissolved Solids
TDS stands for Total Dissolved Solids.
The term refers to the total amount of dissolved material in water.
TDS is usually expressed in ppm or mg/L.
There is an important detail, however.
Many handheld TDS pens do not directly analyse all the substances in the water.
They first measure electrical conductivity, then use a particular factor to convert that reading into an estimated TDS value.
The number displayed on a TDS pen therefore does not explain the water's mineral composition on its own.
Conductivity: EC
EC stands for Electrical Conductivity.
It describes the ability of water to conduct an electric current.
It is usually measured in µS/cm.
Ions in the water contribute to conductivity.
A conductivity measurement does not, however, identify each ion or tell you how much of it is present.
Comparing the Measurements
Parameter
What does it tell you?
What does it not tell you?
GH
General hardness
The separate amounts of calcium and magnesium
KH
Alkalinity and buffering capacity
The exact pH
TDS
A measurement or estimate of total dissolved solids
The substances' chemical composition
EC
Electrical conductivity
Which ions are present
pH
The water's acidity or alkalinity
The complete mineral balance
NeoMa note: Measuring TDS alone is not enough in a shrimp aquarium. GH, KH and conductivity should be considered together, particularly when preparing new water.
The Difference Between TDS and Conductivity
These measurements are often confused in shrimp breeding.
One device might display 150 ppm TDS while another shows conductivity of 300 µS/cm.
Depending on the conversion factor, the two readings could describe the same water.
Some TDS meters use a conversion factor of approximately 0.5.
In that case:
300 µS/cm × 0.5 ≈ 150 ppm
Not every meter uses the same factor.
Other devices may use different conversion factors.
Two breeders simply saying “TDS 150” therefore does not establish that their water has the same properties.
Why Can the Same TDS Produce Different Results?
Suppose two separate water samples both have a TDS reading of 150 ppm.
The first may have been prepared with a suitable shrimp mineral mixture containing calcium and magnesium.
The second may display the same TDS because of other dissolved salts.
Even if the displayed number is identical, the two samples do not necessarily have the same biological suitability.
TDS is therefore a useful monitoring measurement during water preparation, rather than a mineral recipe in its own right.
Can You Use the Same Water for Caridina and Neocaridina?
A single water preparation recipe should not be applied to all Caridina and Neocaridina shrimp.
Soft-water bee-type Caridina lines and common Neocaridina davidi colonies in particular may be bred under different conditions.
The following values are approximate starting ranges for planning their care.
Parameter
Bee-type Caridina
Neocaridina davidi
Temperature
20–23 °C
22–25 °C
pH
Approximately 5.5–6.5
Approximately 6.8–7.8
GH
4–6 °dGH
6–12 °dGH
KH
0–1 °dKH
2–8 °dKH
Mineral approach
Usually GH+
GH+ or GH/KH+, depending on source water
Substrate
Frequently active substrate
Inert or other suitable substrates
These ranges are not experimentally established universal optimums for every species and breeding line.
For specialised Caridina lines in particular, find out the water conditions in which the colony was raised.
Why Is Low KH Preferred for Caridina?
Many bee-type Caridina colonies are bred in low-alkalinity, slightly acidic water.
Preparing low-KH water for an aquarium with active substrate can help the substrate maintain the intended chemistry.
Repeated additions of high-KH water can diminish the substrate's chemical effect.
Why Is the Approach Different for Neocaridina?
Under common breeding conditions, Neocaridina davidi can adapt to a wider range of water parameters than bee-type Caridina.
This does not mean that Neocaridina are unaffected by water changes.
Avoiding sudden changes and establishing stable conditions matter for both groups.
The Difference Between GH+ and GH/KH+ Minerals
Choose the correct mineral product when preparing RO water for shrimp.
Although mineral mixtures are sold under many names, they generally follow two main approaches.
GH+ Minerals
GH+ products are used to increase general hardness.
They generally contain compounds that supply calcium and magnesium.
Their actual ingredients and ion ratios can vary between brands.
This approach is frequently chosen for bee-type Caridina aquariums intended to maintain low KH.
GH/KH+ Minerals
GH/KH+ products are formulated to raise alkalinity as well as general hardness.
They can be used in some Neocaridina systems.
A product being suitable for Neocaridina does not make it essential for every Neocaridina colony.
The source water's existing GH and KH must also be considered.
Which Should You Choose?
Bee-type Caridina aquarium: If low KH is the goal, consider a suitable GH+ product.
Neocaridina aquarium: Choose a suitable product according to the source water and intended GH/KH balance.
Important: The words “shrimp minerals” on a label are not enough. Check the product's effects on GH and KH.
How Do You Remineralise RO Water?
Now let us move to the practical process.
You do not need a specialist laboratory to prepare RO water. You do, however, need reliable measurements and a repeatable method.
Equipment You Need
An RO unit or RO water from a verified source.
A clean preparation container reserved for aquarium use.
A suitable mineral product.
A GH test kit.
A KH test kit.
A conductivity meter or a TDS meter with a known conversion factor.
A thermometer.
Accurate scales, if required.
Equipment for mixing.
The preparation container must not be contaminated with detergent, cleaning agents or other chemicals.
Step 1: Check the RO Water
First measure the water coming out of the RO unit.
Higher-than-expected output conductivity may indicate a need to check membrane performance or system maintenance.
The suitability of RO water cannot be established from a single TDS value alone, however.
The source water's quality and the unit's maintenance condition also matter.
Step 2: Set a Target GH
Choose a target GH according to the needs of your shrimp.
For example, suppose you are aiming for GH 5 °dGH for your bee-type Caridina colony.
This is simply a practical example.
Step 3: Read the Mineral Product's Dosage
Read the manufacturer's dosage information.
Check which GH the product is intended to achieve in a given volume of water.
Mineral concentrations may differ between brands.
Step 4: Dissolve the Minerals in a Separate Container
Add the measured amount of minerals to the preparation container.
Mix thoroughly and allow it to dissolve according to the product's instructions.
Do not pour the mineral powder directly into the aquarium containing shrimp.
Step 5: Measure GH and KH
Measure the GH of the prepared water.
Confirm that KH is at the intended level.
Using the wrong mineral product can have unwanted consequences, especially in low-KH Caridina aquariums.
Step 6: Measure Conductivity
Record the conductivity of the prepared water.
For subsequent batches made with the same mineral product, this reading helps you check consistency.
It is not a reason to abandon GH and KH testing entirely.
Step 7: Match the Temperature
Bring the new water close to the aquarium's temperature.
Avoid large temperature differences, especially in small aquariums.
Step 8: Add the Water in a Controlled Way
Once the final measurements have been confirmed, add the prepared water to the aquarium.
For sensitive colonies, choose a controlled addition method that reduces abrupt changes.
How Much Mineral Do You Add to 5 Litres of RO Water?
This is one of the most common questions in shrimp keeping.
There is, however, no single universally correct number of grams to add to 5 litres of RO water.
Mineral products differ in ingredients and concentration.
We can nevertheless demonstrate how to calculate a dose using an example.
Example Calculation
Purely as an example, suppose a mineral product's label states:
3 grams of minerals for 20 litres of water.
The theoretical amount required for 5 litres to reach the same target is:
3 × 5 / 20 = 0.75 grams
This simply scales the example label's dosage mathematically.
Do not use the same amount for a different product.
After adding the calculated amount, measure GH and conductivity.
Example Table for Different Volumes
Based solely on the hypothetical product above, dosed at 3 grams per 20 litres:
Water to prepare
Calculated minerals
5 litres
0.75 grams
8 litres
1.20 grams
10 litres
1.50 grams
15 litres
2.25 grams
20 litres
3.00 grams
Warning: This table is not a dosage recommendation for an actual mineral product. It is intended only to demonstrate the calculation.
In practice, follow the product label and verify the prepared water by testing it.
Can You Mix RO Water With Tap Water?
Yes. In some circumstances, mixing RO and tap water can bring hardness closer to the target.
The method involves more than a hardness calculation, however.
Chlorine, chloramine, nitrate, metal ions and other substances in tap water must be assessed separately.
For sensitive Caridina colonies in particular, RO water prepared with suitable mineral products may offer greater control.
Calculating the GH of a Mixture
The approximate GH of two mixed waters can be calculated from their volumes using:
Target GH = [(Water 1 GH × Water 1 volume) + (Water 2 GH × Water 2 volume)] / Total volume
This represents a simplified situation in which hardness-contributing substances do not precipitate or undergo another chemical change during mixing.
Example: Obtaining GH 6 From GH 12 Tap Water
Suppose we have two waters:
Tap water: GH 12 °dGH.
RO water: GH approximately 0 °dGH.
We want to prepare 10 litres at GH 6 °dGH.
Approximately:
5 litres of tap water + 5 litres of RO water = 10 litres of mixed water.
Calculation:
(12 × 5 + 0 × 5) / 10 = 6 °dGH
This is a theoretical starting calculation.
Measure GH again after preparing the mixture.
Limitations of This Method
Diluting tap water with RO water:
Does not automatically make chlorine or chloramine safe.
Does not eliminate nitrate completely.
Does not guarantee the absence of unwanted contaminants.
Does not allow the mixture's pH to be calculated as a simple average.
pH in particular is a logarithmic scale.
Mixing equal amounts of pH 6 water and pH 8 water therefore does not automatically produce pH 7 water.
Is RO Water the Same as Water From a Household Softener?
No.
This is an important distinction.
Some household water softeners work through ion exchange.
For example, calcium and magnesium ions may be replaced with sodium ions.
This can lower GH.
It does not mean that the water has become low in ions in the way water from an RO unit does.
Its sodium content may have increased.
Do not assume that water from a household softener is suitable for shrimp simply because its GH is low.
NeoMa recommendation: Find out how your treatment system works. Do not assume a source is suitable for shrimp breeding merely because it is labelled “purified water”.
How Should Prepared RO Water Be Used for Water Changes?
When changing water in a shrimp aquarium, prepare the replacement water to match the existing aquarium conditions as closely as possible.
Suppose, for example, that we have a 40-litre Caridina aquarium.
Its GH is 5 °dGH.
Prepare the replacement water to the same target.
Matching GH alone is not enough, however.
Temperature, KH and conductivity should also be checked.
How Much Water Should Be Changed?
There is no single weekly water-change percentage that applies to every shrimp aquarium.
Requirements depend on:
Aquarium volume.
Number of shrimp.
Amount of food supplied.
Filtration capacity.
Accumulation of nitrate and other waste.
Plant density.
Stability of water parameters.
In a stable aquarium, for example, changing approximately 10–15% weekly can be a starting maintenance plan.
This percentage is not compulsory.
Denser colonies or systems with greater waste accumulation may need different routines.
Are Large Water Changes Harmful?
A large water change is not necessarily harmful in itself.
The main risk is a substantial temperature or chemical difference between the new water and the aquarium water.
For sensitive shrimp colonies in particular, base maintenance on measurements rather than making unplanned large changes.
Should You Add Minerals When Replacing Evaporated Water?
Usually not.
During evaporation, water itself leaves the system.
Most dissolved minerals remain in the aquarium.
Repeatedly topping up evaporation with remineralised water can therefore cause minerals to accumulate over time.
Example: 2 Litres Evaporate From a 40-Litre Aquarium
Suppose the aquarium initially contains 40 litres.
After 2 litres evaporate, 38 litres remain.
Assuming the amount of dissolved minerals has not changed, the concentration increases by a factor of approximately:
40 / 38 = 1.053
That is an increase of approximately 5.3%.
This calculation shows only the effect of evaporation. Mineral uptake by animals, feeding and other processes may also occur in the aquarium.
Replacing the missing 2 litres with suitable low-mineral water reduces the concentration increase caused by evaporation.
How This Differs From a Water Change
Evaporation: Water leaves, while most minerals remain.
Water change: Some water and its dissolved substances are removed together.
For a water change, replacement water should therefore be prepared with suitable mineral content.
For topping up evaporation, low-mineral water is generally preferred.
Can You Use an Automatic Top-Off System?
Yes.
Automatic top-off systems can be useful, especially in open aquariums or systems with substantial evaporation.
They must operate reliably, use the correct water source and have protection against overfilling.
The Most Common RO Water Preparation Mistakes
1. Using RO Water Without Adding Minerals
Low-mineral water should be prepared to meet the shrimp's needs.
2. Targeting Only a TDS Reading
TDS alone does not reveal mineral composition.
3. Choosing the Wrong Mineral Product
GH+ and GH/KH+ products have different purposes.
4. Assuming Different Brands Have the Same Dosage
One gram of one product may not have the same mineral effect as one gram of another.
5. Pouring Minerals Directly Into the Aquarium
This can temporarily create areas of locally high mineral concentration.
6. Using Water Without Measuring GH
Test the actual result after adding minerals.
7. Topping Up Evaporation With Remineralised Water
This can cause dissolved substances to accumulate over time.
8. Not Checking the New Water's Temperature
Sudden temperature changes can cause problems, particularly in small aquariums.
9. Ignoring the Active Substrate's Effect
Active substrate can influence the chemical properties of the prepared water.
10. Deciding From a Single Measurement
When a result is unexpected, check the meter, test kit and preparation method together.
How Do You Troubleshoot RO Water Preparation?
When measurements do not match expectations, adding more minerals is not the first solution.
First identify where the problem comes from.
Observation
Possible causes
First check
RO output conductivity has risen
Membrane performance, changes in feed water, unit maintenance
RO feed and output measurements
GH remains low
Insufficient minerals, dosage or measurement error
Product label and GH test
GH is on target but conductivity is high
Other ions, additives or measurement differences
Water source and products used
KH is higher than expected
Wrong mineral product, tap-water mixture
GH/KH+ use and source water
Aquarium GH rises over time
Remineralised top-off water, dissolving decor
Evaporation and decor
pH rises over time
Declining active-substrate effect, KH input
KH, substrate and replacement water
Shrimp become restless after a water change
Temperature or chemical differences
Measurements of old and new water
If several shrimp behave abnormally at the same time, also check ammonia, nitrite, oxygenation and possible chemical contaminants.
How Long Should Prepared Water Be Left Standing?
There is no single answer in hours.
The time required depends on the mineral product's dissolution properties and the preparation method.
What matters is that:
The minerals have dissolved completely.
The water is mixed evenly.
GH and, where necessary, KH have been verified.
The conductivity reading has stabilised.
Temperature is suitable for the aquarium.
The water being used is known to be safe.
If the minerals are dissolved and measurements have been verified, there is no need to leave water standing unnecessarily just to meet an arbitrary waiting time.
Do not, however, rush to use a mixture that has not finished dissolving.
How Should Water Preparation Be Recorded in NeoMa?
If you obtain different results every week for the same aquarium, mineral quantity may not be the only cause.
Recording the preparation process makes it easier to understand where changes originate.
For each water change, for example, you can record:
Record
Example
Date
31 October
Aquarium
Caridina breeding tank
Prepared water
5 litres
Water source
RO
Mineral type
GH+
Target GH
5 °dGH
Measured GH
5 °dGH
KH
0–1 °dKH
Conductivity
Measured value in µS/cm
Temperature
22 °C
Observation
Normal behaviour
These records make it easier to repeat the same method for later batches.
If a problem develops in the colony, you can also review which changes were made.
Frequently Asked Questions
Is RO Water Essential for a Shrimp Aquarium?
Not every shrimp aquarium needs it. For soft-water bee-type Caridina colonies in particular, however, it can make water preparation more controlled.
Can RO Water Be Added Directly to the Aquarium?
It should not be used as the main replacement water without establishing the mineral balance the shrimp need. Topping up evaporation is a different task.
Should You Use GH+ or GH/KH+ for Caridina?
Suitable GH+ products are generally preferred for bee-type Caridina aquariums intended to maintain low KH.
Which Minerals Should You Use for Neocaridina?
Consider GH+ or GH/KH+ according to the source water's existing GH and KH.
Is Water Ready When TDS Reaches 150?
No. TDS alone does not establish mineral composition or suitability for shrimp.
Are GH and TDS the Same Thing?
No. GH relates to general hardness, while TDS describes total dissolved solids.
How Many Grams of Minerals Go Into 5 Litres of RO Water?
It depends on the mineral product and target GH. There is no universal amount in grams.
Why Can RO Water's pH Vary?
In low-alkalinity water, pH is easily affected by dissolved carbon dioxide and measurement conditions. Interpreting RO water's pH on its own can therefore be misleading.
Should Minerals Be Added When Replacing Evaporated Water?
Under normal conditions, evaporation is topped up with suitable low-mineral water because most minerals remain in the aquarium.
Can Prepared Remineralised Water Be Stored?
It can be stored in clean, suitable containers. Before use, recheck mixing uniformity, temperature and the necessary water parameters.
Can RO Water Be Mixed With Tap Water?
Yes, when the source water is suitable. A GH calculation alone is not enough; consider the tap water's other components and any necessary treatment.
Conclusion: Good Water Preparation Means Reproducing the Same Conditions
The purpose of RO water in a shrimp aquarium is not simply to achieve a low TDS.
It is to build a mineral composition suited to the shrimp in a controlled way and maintain those conditions throughout their care.
Remember three key points:
First: RO water is starting water; the appropriate mineral balance must be prepared separately.
Second: GH, KH and conductivity provide different information. One measurement does not replace the others.
Third: Water changes and evaporation top-offs are different tasks.
For sensitive Caridina colonies in particular, repeating a successful preparation method is a healthier approach than experimenting with a random new value at every water change.
By regularly recording water changes and parameters in NeoMa, you can follow changes in your aquarium and base care decisions on measurements rather than guesses.
Scope of the sources: The USGS and EPA sources support the basic water chemistry concepts. Mineral doses and mixing calculations in this guide are explanatory practical examples, not experimentally established optimum values for a particular shrimp line.
