Introduction
Water parameters are the measurable chemical and physical properties of aquarium water that directly impact the health and wellbeing of aquatic life. Maintaining appropriate water parameters is the foundation of successful fishkeeping, as even small fluctuations can stress or harm fish and invertebrates. This cheat sheet provides a comprehensive guide to understanding, testing, and maintaining optimal water conditions for both freshwater and saltwater aquariums.
Core Water Parameters
Essential Parameters for All Aquariums
| Parameter | Freshwater Range | Saltwater Range | Testing Frequency | Impact |
|---|---|---|---|---|
| Temperature | 72-82°F (22-28°C) | 75-82°F (24-28°C) | Daily | Metabolism, immune function, breeding |
| pH | 6.5-8.0 | 8.1-8.4 | Weekly | Enzyme activity, toxicity of compounds |
| Ammonia (NH₃) | 0 ppm | 0 ppm | Weekly/Cycling | Highly toxic, burns gills, inhibits respiration |
| Nitrite (NO₂) | 0 ppm | 0 ppm | Weekly/Cycling | Toxic, binds to hemoglobin, causes “brown blood disease” |
| Nitrate (NO₃) | <20 ppm | <5 ppm | Weekly | Stresses fish at high levels, promotes algae growth |
| Dissolved Oxygen | >5 ppm | >5 ppm | As needed | Fish respiration, beneficial bacteria function |
Freshwater-Specific Parameters
| Parameter | Soft Water Range | Medium Range | Hard Water Range | Importance |
|---|---|---|---|---|
| GH (General Hardness) | 3-6 dGH | 7-12 dGH | 13-20+ dGH | Osmotic regulation, breeding, plant growth |
| KH (Carbonate Hardness) | 3-5 dKH | 6-10 dKH | 11-15+ dKH | pH stability, plant growth |
| TDS (Total Dissolved Solids) | 50-150 ppm | 150-300 ppm | 300-450+ ppm | Osmotic pressure, breeding triggers |
Saltwater-Specific Parameters
| Parameter | Optimal Range | Testing Frequency | Impact |
|---|---|---|---|
| Salinity/Specific Gravity | 1.023-1.025 (35 ppt) | Daily/Weekly | Osmotic balance, coral health |
| Calcium | 380-450 ppm | Weekly | Coral/invertebrate skeletal growth |
| Alkalinity | 7-12 dKH | Weekly | pH stability, coral growth |
| Magnesium | 1250-1350 ppm | Monthly | Supports calcium utilization, coral health |
| Phosphate | <0.05 ppm | Weekly | Limits nuisance algae, coral health |
| Silicate | <1.0 ppm | Monthly | Prevents diatom blooms |
| Iodine | 0.06-0.10 ppm | Monthly | Invertebrate health, molting |
| Strontium | 8-14 ppm | Monthly | Coral skeletal development |
Understanding the Nitrogen Cycle
Cycle Stages
Ammonia Production (NH₃/NH₄⁺)
- Source: Fish waste, uneaten food, decaying matter
- Safe Level: 0 ppm
- Time to Appear: Immediate
Nitrite Production (NO₂)
- Source: Converted from ammonia by Nitrosomonas bacteria
- Safe Level: 0 ppm
- Time to Appear: 1-2 weeks into cycling
Nitrate Production (NO₃)
- Source: Converted from nitrite by Nitrobacter bacteria
- Safe Level: <20 ppm freshwater, <5 ppm saltwater
- Time to Appear: 3-4 weeks into cycling
Cycling Methods Comparison
| Method | Time Required | Pros | Cons |
|---|---|---|---|
| Fish-In Cycling | 4-8 weeks | Can be done with new fish | Stressful to fish, requires frequent water changes |
| Fishless (Ammonia) | 3-6 weeks | No risk to fish, controlled | Requires pure ammonia source, daily testing |
| Seeded Media | 1-3 weeks | Fastest method | Requires access to established tank media |
| Bottled Bacteria | 1-4 weeks | Convenient | Variable effectiveness between brands |
Testing Methods & Accuracy
Testing Options Comparison
| Test Type | Accuracy | Cost | Ease of Use | Best For |
|---|---|---|---|---|
| Test Strips | Low-Medium | $ | Very Easy | Quick checks, general trends |
| Liquid Test Kits | High | $$ | Moderate | Regular maintenance, troubleshooting |
| Digital Meters | Very High | $$$ | Easy | Specific parameters (pH, TDS) |
| Lab Testing | Highest | $$$$ | Requires shipping | Specialized parameters, verification |
Testing Best Practices
- Test at the same time of day (preferably before feeding)
- Follow instructions precisely regarding time to read results
- Check expiration dates on test kits
- Rinse test tubes thoroughly between tests
- Store test kits away from heat and light
- Calibrate digital meters regularly
pH Management
Common pH Adjusters
| Method | Direction | Speed | Stability | Best For |
|---|---|---|---|---|
| Driftwood/Botanicals | Lowers pH | Slow | Good | Blackwater/Amazon biotopes |
| Limestone/Crushed Coral | Raises pH | Moderate | Excellent | African cichlid tanks |
| Chemical pH Up/Down | Both | Fast | Poor | Emergency corrections only |
| Peat Moss | Lowers pH | Slow | Good | Soft water species |
| Baking Soda | Raises pH | Fast | Moderate | KH/pH emergency increase |
| CO₂ Injection | Lowers pH | Fast | Poor | Planted tanks (daytime only) |
pH Stability Tips
- Maintain adequate KH (3+ dKH) to buffer pH changes
- Perform smaller, more frequent water changes
- Match source water to tank parameters
- Avoid overstocking and overfeeding
- Choose appropriate substrate for desired pH
Water Hardness Guide
Species Preferences
| Fish Type | Preferred GH | Preferred KH | Ideal pH |
|---|---|---|---|
| Amazonian (Tetras, Discus) | 3-8 dGH | 3-5 dKH | 6.0-7.0 |
| Southeast Asian (Bettas, Gouramis) | 4-10 dGH | 3-8 dKH | 6.5-7.5 |
| African Cichlids (Malawi, Tanganyika) | 12-20 dGH | 10-15 dKH | 7.8-8.6 |
| Livebearers (Mollies, Guppies) | 10-15 dGH | 8-12 dKH | 7.0-8.0 |
| Goldfish | 5-19 dGH | 4-12 dKH | 7.0-8.4 |
| Shrimp (Neocaridina) | 6-14 dGH | 2-5 dKH | 6.8-7.5 |
| Shrimp (Caridina) | 4-6 dGH | 0-2 dKH | 6.0-6.8 |
Hardness Modification Methods
| Method | Effect | Duration | Notes |
|---|---|---|---|
| RO/DI Water | Removes all minerals | Permanent | Requires remineralization |
| Water Softening Pillow | Reduces GH | Temporary | Must be recharged |
| Peat/Catappa Leaves | Softens water slightly | Temporary | Also reduces pH |
| Crushed Coral/Aragonite | Increases GH/KH | Long-term | Dissolves slowly as needed |
| Wonder Shells | Increases GH/KH | Medium-term | Dissolves over weeks |
| Mineral Supplements | Increases GH/KH | Immediate | Can be precisely dosed |
Specialized Parameters for Advanced Tanks
Planted Tank Parameters
| Parameter | Optimal Range | Testing Frequency | Impact |
|---|---|---|---|
| CO₂ | 15-30 ppm | Daily | Plant growth, pH stability |
| Iron | 0.1-0.5 ppm | Weekly | Leaf development, chlorophyll production |
| Potassium | 10-20 ppm | Weekly | Plant metabolism, disease resistance |
| Phosphate | 0.5-2.0 ppm | Weekly | Plant growth, algae control |
| Nitrate | 5-20 ppm | Weekly | Plant growth, algae control |
Reef Tank Parameters
| Parameter | Optimal Range | Testing Frequency | Impact |
|---|---|---|---|
| Calcium | 400-450 ppm | Weekly | Coral skeletal growth |
| Alkalinity | 8-12 dKH | Twice weekly | Coral growth, pH stability |
| Magnesium | 1280-1350 ppm | Bi-weekly | Calcium/alkalinity stability |
| Potassium | 380-420 ppm | Monthly | Coral coloration, growth |
| Strontium | 8-14 ppm | Monthly | Coral skeletal structure |
| Iodine | 0.06-0.08 ppm | Bi-weekly | Invertebrate health, coral coloration |
| Silicate | <0.03 ppm | Monthly | Prevents diatom blooms |
| ORP (Redox) | 300-400 mV | Weekly | Water quality indicator |
Common Problems & Solutions
pH Issues
| Problem | Possible Causes | Solutions |
|---|---|---|
| pH Crash | Low KH, high bioload, CO₂ buildup | Increase aeration, add buffer, water change |
| pH Swing | Inadequate buffering, CO₂ fluctuation | Increase KH, stabilize CO₂, check lighting period |
| pH Too High | Decorations leaching minerals, hard tap water | Use RO water, add botanicals, use pH-lowering substrate |
| pH Too Low | Acidic substrate, driftwood, CO₂ injection | Add crushed coral, use buffer, increase water changes |
Ammonia/Nitrite Problems
| Problem | Possible Causes | Solutions |
|---|---|---|
| Ammonia Spike | New tank, overstocking, overfeeding | Water changes, reduce feeding, add cycled media |
| Persistent Nitrite | Incomplete cycle, medication killing bacteria | Patience, water changes, add bottled bacteria |
| Nitrate Buildup | Inadequate water changes, overcrowding | Increase water changes, add plants, reduce stocking |
| Stalled Cycle | pH issues, chlorine, medications | Check pH, use dechlorinator, stop medications |
Water Hardness Problems
| Problem | Possible Causes | Solutions |
|---|---|---|
| GH Too High | Hard tap water, mineral-rich substrate | Use RO water, blend with soft water, use softening pillow |
| KH Too Low | Soft tap water, acidic substrate | Add crushed coral, use buffer product, aragonite sand |
| Unstable Parameters | Low buffering capacity | Increase water change frequency, add buffer |
| TDS Creep | Evaporation, treatments, supplements | Regular water changes, use RO water for top-offs |
Best Practices & Tips
Water Change Protocol
- Always use dechlorinator with tap water (double dose for chloramine)
- Match temperature within 2°F of tank water
- Adjust parameters of new water before adding to tank
- Add water slowly to minimize stress
- Test parameters before and after large water changes
Water Source Preparation
| Water Source | Pros | Cons | Best Use |
|---|---|---|---|
| Tap Water | Convenient, inexpensive | May contain chlorine/chloramine, metals | General freshwater tanks |
| RO/DI Water | Pure, parameter control | Requires remineralization, equipment cost | Reef tanks, sensitive species |
| Bottled Water | Convenient, consistent | Expensive, unknown mineral content | Emergency use, small tanks |
| Well Water | No chlorine, often mineral-rich | May contain metals, sulfur, variable | Test thoroughly before use |
| Rainwater | Soft, free | Potential pollutants, inconsistent | Supplement for soft water tanks |
Specialized Equipment
| Equipment | Function | Benefit | Tank Type |
|---|---|---|---|
| pH Controller | Monitors and adjusts pH | Stability for sensitive species | Reef, Discus, Plants |
| KH/Alkalinity Doser | Maintains stable KH | Prevents pH swings | Reef |
| Calcium Reactor | Dissolves calcium media | Stable calcium levels | Reef |
| CO₂ System | Provides carbon for plants | Enhanced plant growth | Planted |
| RO/DI System | Purifies water | Parameter control | Any specialized |
| UV Sterilizer | Kills free-floating algae/bacteria | Clearer water, disease prevention | Any |
Resources for Further Learning
Water Testing Tools
- API Master Test Kits (Freshwater and Saltwater)
- Salifert Test Kits (Reef parameters)
- Hanna Digital Checkers
- Red Sea Reef Foundation Test Kit
- Seachem Ammonia Alert (continuous monitoring)
Apps & Online Calculators
- Aquarium Note (parameter tracking)
- AquaCalc (dosing calculator)
- GHL Control (parameter monitoring)
- Red Sea Foundation Calculator
- ICP Water Analysis Tracker
Educational Resources
- “Water Chemistry & the Aquarium” by Randy Holmes-Farley
- BRS 52 Weeks of Reefing (YouTube series)
- 2hrAquarist.com (planted tank parameters)
- Reef2Reef.com Forums (marine water chemistry)
- The Aquarium Wiki (parameter guides)
Professional Services
- ICP-OES Testing (Triton, ATI)
- Local fish store water testing
- University extension water analysis programs
- Environmental testing labs (for source water)
Remember: Stability is more important than perfect parameters. Small, consistent adjustments are always better than dramatic changes that can stress aquatic life.