What is pH?
pH measures how acidic or alkaline your water is on a scale of 0-14. A pH of 7.0 is neutral, below 7 is acidic, and above 7 is alkaline. For shrimp keeping, most species fall between 6.0 and 8.5, but the crucial point isn’t hitting a specific number - it’s maintaining consistency.
The pH scale is logarithmic, meaning each whole number represents a 10x change. Water at pH 6.0 is 10 times more acidic than pH 7.0, and 100 times more acidic than pH 8.0. This is why even small pH swings (0.3-0.5) can stress shrimp significantly.
The Golden Rule: Stability Over Perfection
If you remember only one thing about pH, let it be this: A stable pH of 7.2 is infinitely better than pH swinging between 6.8-7.0 trying to hit “optimal.”
Shrimp are adaptable creatures. Given time, they can adjust their physiology to thrive in a wide pH range. What they cannot do is rapidly adapt to changes. Every pH swing forces their bodies to readjust, consuming energy, stressing their systems, and potentially triggering failed molts.
Why Chasing pH Numbers Fails
New shrimp keepers often make this mistake:
- Test pH, find it’s 7.4 (slightly above “optimal 7.0”)
- Add pH-down chemical to lower it
- pH drops to 6.8, then rebounds to 7.6 as buffer kicks in
- Add more chemical, causing more swings
- Shrimp become stressed or die from instability
The 7.4 starting pH was fine. The “correction” caused the actual problem.
Species-Specific pH Requirements
Neocaridina (Cherry Shrimp, etc.)
Neocaridina prefer neutral to slightly alkaline water (pH 6.8-8.0, optimal 7.0-7.5). Most tap water falls in this range, which is why Neocaridina work well for beginners. Moderate KH (2-8 dKH) provides natural buffering.
Caridina (Crystal Red, Taiwan Bee, etc.)
Caridina require acidic water (pH 5.8-6.8, optimal 6.0-6.5). This is achieved through active buffering substrates that lower pH and maintain it without KH buffering. The substrate itself acts as the pH buffer.
Sulawesi Shrimp
Sulawesi evolved in alkaline ancient lakes and need high pH (7.5-8.5, optimal 7.8-8.2). This requires specific Sulawesi mineral salts that buffer to high pH, combined with appropriate substrate (often sand or inert gravel).
What Affects pH in a Shrimp Tank
Factors That LOWER pH
- CO2 (from respiration, decomposition, or injection)
- Decomposing organic matter
- Nitrification process (bacteria produce acid)
- Active/buffering substrates
- Tannins from driftwood, leaves
- Peat moss filtration
Factors That RAISE pH
- Crushed coral, aragonite, limestone
- Strong aeration (drives off CO2)
- Photosynthesis (plants consume CO2 during daytime)
- High KH water
- Concrete or calcium-based decorations
The pH-KH Connection
pH and KH are intimately linked:
- High KH water resists pH changes - good for stability, but locks in higher pH
- Low KH water allows pH changes - allows lower pH, but needs alternative buffering
- Active substrates work by absorbing KH - this is how they lower and maintain pH
For Neocaridina: Use moderate KH for natural pH buffering For Caridina: Use zero KH with active substrate for low, stable pH For Sulawesi: Use specialized mineral salts that buffer to high pH
Signs of pH Problems
pH Too Low
- Shrimp appear lethargic
- Bacterial infections increase (beneficial bacteria struggle)
- Plants may show poor growth
- Ammonia becomes less toxic but nitrite remains dangerous
pH Too High
- Shell problems (too much calcium carbonate precipitation)
- Ammonia becomes more toxic (important for cycling tanks!)
- Some plants struggle
- Caridina show stress symptoms
pH Instability (The Biggest Danger)
- Deaths with no obvious cause
- Failed molts, White Ring of Death
- Shrimp hiding constantly
- Reduced breeding or berried females dropping eggs
- Deaths concentrated at certain times (often morning after overnight pH drop)
pH by Species Family
Different shrimp families have evolved in different environments, leading to varying ph requirements. Understanding these differences is crucial for successful shrimp keeping.
| Family | Acceptable Range | Optimal Range | Example Species | Notes |
|---|---|---|---|---|
| Neocaridina | 6.8-8 | 7-7.5 | Cherry Shrimp | Hardy, tolerates wider ranges |
| Caridina | 5.8-6.8 | 6-6.5 | Crystal Red Shrimp | Sensitive, requires stable parameters |
| Sulawesi | 7.5-8.5 | 7.8-8.2 | Cardinal Shrimp | Unique requirements, warm alkaline water |
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 pH
Accurate testing is essential for maintaining proper ph levels. Here are the most common testing methods, each with their own trade-offs.
Digital pH Meter
Pros
- Precise digital readings
- Fast results
- Good for frequent testing
Cons
- Requires regular calibration
- Electrode needs proper storage
- More expensive than liquid kits
Liquid Test Kit
Pros
- No calibration needed
- Reliable for range testing
- Long shelf life
Cons
- Color matching can be tricky
- May need high-range and low-range kits
- Less precise than digital
Test Strips
Pros
- Quick and easy
- Good for rough checks
Cons
- Least accurate option
- Color matching issues
- Can't detect small changes
Quick Comparison
| Method | Accuracy | Cost | Best For |
|---|---|---|---|
| Digital pH Meter | High | $$ | Recommended choice |
| Liquid Test Kit | Medium | $ | General use |
| Test Strips | 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 pH
Sometimes you need to adjust your ph 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 pH
Increase ph levels
Crushed Coral/Aragonite
Add to filter or substrate to slowly raise pH through calcium carbonate dissolution
Increase Aeration
More surface agitation drives off CO2, which raises pH
Sulawesi Mineral Salts
For Sulawesi tanks, use specific mineral salts that buffer to high pH
Warnings
- Never chase a specific pH number - stability is more important
- Crushed coral affects KH too - not for Caridina tanks
- Chemical pH adjusters cause instability - avoid them
How to Lower pH
Decrease ph levels
Active Substrate
Buffering substrates like ADA Amazonia naturally lower and stabilize pH
Indian Almond Leaves
Add tannins that slightly lower pH while providing other benefits
RO Water with GH+ Only
Using RO water with no KH contribution helps maintain lower pH
Warnings
- Do NOT use CO2 injection primarily to lower pH for shrimp
- pH-down chemicals cause dangerous instability
- Lower pH needs lower KH for stability (active substrate handles this)
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.
pH FAQ
Shrimp can adapt to a range of pH levels if given time, but they cannot adapt to rapid changes. A stable pH of 7.5 is healthier than pH swinging between 6.8 and 7.2. pH changes stress shrimp, weaken immune systems, trigger bad molts, and can cause sudden deaths. Consistency is always the priority.
Common causes include: low KH (no buffer), CO2 fluctuations (from plants or poor aeration), decomposing organics, irregular water changes, and exhausted active substrate. Even normal biological processes can swing pH if there's insufficient buffering. Test pH at the same time daily to identify patterns.
No. Commercial pH-up and pH-down solutions cause temporary changes that don't last, leading to dangerous swings. They also don't address the underlying cause. Instead, fix pH through proper KH management (for high-pH tanks) or active substrate (for low-pH tanks). These provide stable, lasting results.
Caridina evolved in soft, acidic blackwater streams where pH naturally sits around 6.0-6.5 due to decomposing organic matter. Their physiology is optimized for this environment. Higher pH stresses them and interferes with breeding. Active substrates recreate these natural conditions in the aquarium.
Active substrates contain cation exchange materials that absorb alkaline ions (KH) and release hydrogen ions. This ion exchange lowers pH and maintains it around 6.0-6.5 as long as the substrate has exchange capacity remaining. Eventually (12-24 months typically), the substrate exhausts and pH rises.
During the day, plants photosynthesize and consume CO2, raising pH slightly. At night, plants stop photosynthesis but continue respiring, releasing CO2. This CO2 forms carbonic acid, lowering pH. In well-buffered tanks with adequate KH, these swings are minimal. In low-KH tanks, they can be significant.
Track Your pH with ShrimpKeeper
Stop guessing. Start tracking. ShrimpKeeper gives you species-specific ph ranges, instant diagnostics, and historical graphs for your colony.