What is TDS?
TDS (Total Dissolved Solids) measures the combined content of all dissolved substances in your aquarium water - everything from essential minerals like calcium and magnesium to organic compounds from fish waste and decaying matter. Think of it as a “water heaviness” indicator that gives you a quick snapshot of your water’s overall mineral and organic load.
When you dip a TDS meter into your tank, it measures electrical conductivity and converts that reading to parts per million (ppm). Pure water conducts almost no electricity, but dissolved minerals and salts increase conductivity. This is why RO (reverse osmosis) water reads near 0 ppm - it’s been stripped of nearly all dissolved substances.
Why TDS Matters for Shrimp
Shrimp are osmoregulators, meaning they actively maintain their internal fluid balance against the surrounding water. When TDS is too high, shrimp must work harder to prevent water loss to their environment. When TDS is too low, they struggle to retain essential minerals. This constant balancing act affects:
- Molting success: Proper TDS ensures shrimp have access to minerals needed for new shell formation
- Stress levels: Osmotic stress from incorrect TDS weakens immune systems
- Breeding: Stressed shrimp often stop breeding or produce fewer viable offspring
- Color intensity: Healthy shrimp in optimal conditions display their best coloration
The Caridina Difference
Caridina shrimp (Crystal Red, Taiwan Bee, etc.) evolved in soft, acidic waters with very low mineral content. Their physiology is optimized for TDS ranges of 100-150 ppm. Higher TDS causes chronic osmotic stress that may not kill immediately but leads to failed molts, bacterial infections, and shortened lifespans.
Neocaridina are far more adaptable, having been bred in captivity for decades across various water conditions. They thrive in TDS ranges of 150-300 ppm and can often tolerate even higher levels, making them ideal for beginners using treated tap water.
Signs of TDS Problems
TDS Too High
- Lethargy and reduced activity
- Failed or incomplete molts
- White Ring of Death (incomplete molting)
- Reduced breeding activity
- Deaths shortly after water changes (if new water has even higher TDS)
TDS Too Low
- Soft, fragile shells
- Difficulty molting (insufficient minerals)
- Pale coloration
- Reduced activity
- Poor growth rates in juveniles
Common Mistakes to Avoid
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Chasing exact numbers: A stable TDS of 200 ppm is better than fluctuating between 150-180 ppm trying to hit “optimal”
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Using tap water without testing: Municipal water TDS can vary seasonally and after treatment plant changes
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Ignoring evaporation: As water evaporates, TDS rises because minerals don’t evaporate - top off with pure RO water, not remineralized water
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Mixing species with different needs: Keeping Caridina and Neocaridina together forces a compromise that’s optimal for neither
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Relying solely on TDS: Low TDS doesn’t guarantee proper mineral balance - you can have 150 ppm TDS with no calcium. Always test GH and KH as well
Recommended Remineralizers for TDS Control
The best way to manage TDS in an RO water setup is with quality remineralizers. These products let you achieve precise, repeatable TDS levels:
For Low TDS (Caridina - 100-150 ppm)
- Salty Shrimp Bee Shrimp Mineral GH+ - Precise dosing for Crystal Red and Taiwan Bee
- SL-Aqua Blue Wizard GH - Taiwanese premium option with clean mineral profile
- Brightwell Remineraliz-P - US-made alternative
For Moderate TDS (Neocaridina - 180-250 ppm)
- Salty Shrimp Shrimp Mineral GH/KH+ - Industry standard for Cherry Shrimp
- SL-Aqua MORE SHRIMP! GH/KH - Premium alternative with consistent results
Budget Options
- NilocG GH Booster - Best value for large tanks
- DIY GH Booster - Most economical for experienced keepers
View All Remineralizers to compare products and find dosing guides.
Helpful Calculators
Need help with TDS management? Try these free calculators:
- Remineralization Calculator - Calculate exact remineralizer doses for your RO water
- Water Change Calculator - Determine water change percentage to reach target TDS
- TDS Adjustment Calculator - Get step-by-step instructions for raising or lowering TDS
TDS by Species Family
Different shrimp families have evolved in different environments, leading to varying tds requirements. Understanding these differences is crucial for successful shrimp keeping.
| Family | Acceptable Range | Optimal Range | Example Species | Notes |
|---|---|---|---|---|
| Neocaridina | 150-300 ppm | 180-220 ppm | Cherry Shrimp | Hardy, tolerates wider ranges |
| Caridina | 100-150 ppm | 120-140 ppm | Crystal Red Shrimp | Sensitive, requires stable parameters |
| Sulawesi | 150-250 ppm | 180-220 ppm | Cardinal Shrimp | Unique requirements, warm alkaline water |
Hardy, tolerates wider ranges
Sensitive, requires stable parameters
Unique requirements, warm alkaline water
Stability Over Perfection
While hitting optimal ranges is ideal, stability is more important than exact numbers. Consistent parameters within the acceptable range are better than fluctuating values that occasionally hit optimal.
How to Test TDS
Accurate testing is essential for maintaining proper tds levels. Here are the most common testing methods, each with their own trade-offs.
TDS Meter (Digital Pen)
Pros
- Instant digital readings
- Easy to use - just dip and read
- Reusable with minimal maintenance
- Affordable ($10-30)
Cons
- Requires periodic calibration
- Measures total dissolved solids, not specific minerals
- Battery replacement needed
Calculation from GH/KH
Pros
- No additional equipment if you already test GH/KH
- Provides rough estimate
Cons
- Inaccurate - only estimates hardness minerals
- Misses organics and other dissolved substances
- Not recommended for precise adjustments
Quick Comparison
| Method | Accuracy | Cost | Best For |
|---|---|---|---|
| TDS Meter (Digital Pen) | High | $ | Recommended choice |
| Calculation from GH/KH | Low | $ | Quick checks |
Testing Tip
Test at the same time of day for consistent results. Water parameters can fluctuate based on feeding, lighting, and CO2 levels. Morning tests before lights-on often provide the most stable readings.
How to Adjust TDS
Sometimes you need to adjust your tds levels. Here are safe methods for both raising and lowering values. Always make changes gradually - sudden parameter swings can stress or kill shrimp.
How to Raise TDS
Increase tds levels
Add Remineralizer
Mix appropriate remineralizer (Salty Shrimp GH+, GH/KH+, or Sulawesi Mineral 8.5) into RO water before adding to tank
Reduce Water Change Volume
Smaller, more frequent water changes allow natural mineral buildup from feeding and waste
Add Mineral Stones
Place mineral stones or crusite in the tank for slow mineral release
Warnings
- Never add dry remineralizer directly to a tank with shrimp
- Always premix in a separate container and match temperature
- Raise TDS slowly - no more than 20-30 ppm per day
How to Lower TDS
Decrease tds levels
Dilute with RO/DI Water
Replace portion of tank water with pure RO or DI water to lower total dissolved solids
Larger Water Changes
More frequent water changes with lower-TDS replacement water
Reduce Feeding
Less food means less waste breakdown contributing to TDS
Warnings
- Never replace more than 20-25% of water at once
- Match temperature of new water to tank water
- Lower TDS gradually to avoid osmotic shock
Critical Safety Notice
Never make sudden, large changes to water parameters. Shrimp are extremely sensitive to parameter swings. All adjustments should be made gradually over hours or days, not minutes. When in doubt, go slower. Test frequently during adjustments to monitor progress.
TDS FAQ
TDS (Total Dissolved Solids) measures the total concentration of all dissolved substances in water, including minerals (calcium, magnesium), salts, metals, and organic matter. It's measured in parts per million (ppm) or milligrams per liter (mg/L), which are equivalent. TDS gives you a quick overall picture of water 'heaviness' but doesn't tell you what specific substances are dissolved.
Caridina shrimp evolved in soft, mineral-poor waters and have adapted to regulate their internal osmotic pressure in low-TDS environments. Higher TDS creates osmotic stress, making it harder for them to maintain proper fluid balance. Neocaridina are more adaptable and can handle the wider TDS ranges found in typical tap water.
TDS being in range doesn't guarantee safe water. Tap water can contain chlorine, chloramine, copper, and other substances harmful to shrimp even at low TDS. Always dechlorinate tap water and test for heavy metals. Many successful Neocaridina keepers use treated tap water, but Caridina generally require RO water remineralized to exact specifications.
Test TDS weekly as part of your regular maintenance routine, and always before and after water changes. TDS naturally rises between water changes due to evaporation (water leaves, minerals stay) and waste breakdown. If you notice rapid TDS increases, investigate potential causes like overfeeding or decaying plant matter.
Rising TDS between water changes is normal due to evaporation and waste breakdown. However, rapid increases can indicate overfeeding, dead/decaying organisms, excess fertilizer dosing, or substrate breakdown. Check for dead shrimp or snails, reduce feeding, and ensure your tank isn't overcrowded.
GH and KH contribute to TDS but don't account for all of it. TDS includes everything dissolved - GH minerals (calcium, magnesium), KH carbonates, plus organics, nitrates, and other substances. You can have high TDS with low GH if there are many non-hardness minerals present. This is why testing both TDS and GH/KH is important.
RO water isn't required for most Neocaridina if your tap water parameters are suitable (TDS 150-350, GH 6-15, no copper/chloramine). However, RO water gives you complete control over mineral content. If your tap water is inconsistent or borderline, RO + remineralizer provides more stable conditions.
Track Your TDS with ShrimpKeeper
Stop guessing. Start tracking. ShrimpKeeper gives you species-specific tds ranges, instant diagnostics, and historical graphs for your colony.
TDS Problems & Troubleshooting
Berried Shrimp Dropping Eggs
MediumWhy female shrimp release their eggs prematurely and what you can do to save the eggs or prevent future egg drops.
Failed Molt: Shrimp Stuck in Shell
CriticalUnderstanding failed molts where shrimp cannot escape their old exoskeleton. Learn why it happens, why affected shrimp cannot be saved, and how to prevent future molt failures.
Shrimp Dying After Water Change
HighWhy shrimp die within hours or days after a water change, and how to perform safe water changes that won't stress or kill your colony.
Why Are My Shrimp Dying?
CriticalComprehensive triage guide for unexplained shrimp deaths. Learn to identify the cause and take immediate action to save your remaining colony.