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Planted Aquarium Chemistry
THE ULTIMATE GUIDE
Every healthy ecosystem requires a balanced environment. Weekly water tests are invaluable to making sure your aquarium’s levels are in check. Understanding water chemistry and maintaining optimum levels of key nutrients, minerals and other indicators will protect aquatic life and allow the organisms in your care to thrive and radiate. Below are the key parameters to monitor for planted freshwater aquaria.
Periodic Table of Reef Elements | Aqua Lab Aquaria
Use the following information to help you decipher your test results.
Please keep in mind this is a general guide for planted tanks and specific requirements can vary by species. Please do additional research before attempting any of the methods outlined here. Click bold words for more info.
AMMONIA
Target Value: 0
Ammonia is a toxic nitrogenous compound released when anything organic breaks down. A large amount of decomposition (e.g. from a corpse or uneaten food) can cause ammonia to spike. Specialized bacteria convert ammonia to nitrite.
Ammonia | Aqua Lab Aquaria
TOO MUCH
Ammonia levels above 0.25 ppm can suffocate fish and invertebrates in a matter of hours. It is typically present in new tanks and should be cycled out completely before animals are introduced incrementally. Ways to decrease:
TOO LITTLE
No issues arise from too little ammonia, except when cycling a new tank. Ammonia is necessary at first to fuel the development of bacteria that convert ammonia to nitrite. Ways to increase:
  • Add a carbon source (e.g. food, animal waste, or other organic matter) and allow to decompose
  • Start a new tank with nutrient-rich soil such as ADA Amazonia
NITRITE
Target Value: 0
Nitrite is a toxic nitrogenous compound produced by bacteria as part of the nitrogen cycle. Specialized bacteria convert nitrite to nitrate.
Ammonia | Aqua Lab Aquaria
TOO MUCH
Nitrite will reduce the amount of oxygen in fish's blood, and levels above 1 ppm can be lethal in a matter of hours. It is typically present in new tanks and should be cycled out completely before animals are introduced incrementally. Ways to decrease:
TOO LITTLE
No issues arise from too little nitrite.
NITRATE
Target Value: 5 - 15 ppm, 25 ppm maximum
The last and least toxic of the nitrogenous compounds, this nutrient encourages plant growth and is beneficial in small amounts. It is converted from nitrite by specialized bacteria.
Ammonia | Aqua Lab Aquaria
TOO MUCH
Nitrate levels above 30 ppm can be lethal to aquatic animals in a matter of hours. More nitrate will also lead to more algae growth. Ways to decrease:
TOO LITTLE
A lack of nutrients will inhibit plant growth. While this might enhance coral color, it will also result in coral fragility since coral won't be able to derive glucose and essential amino acids from the algae. Ways to increase:
PHOSPHATE
Target Value: 0.5 - 1 ppm
Phosphate is a nutrient that supports photosynthesis, a vital process for plants.
Ammonia | Aqua Lab Aquaria
TOO MUCH
Too much phosphate is generally not a concern, but it can promote excess algae growth. Ways to decrease:
TOO LITTLE
A lack of phosphate will inhibit plant growth. While dosing potassium phosphate would increase only phosphate, it would usually be better to increase nutrients, like so:
CARBONATE & BICARBONATE (KH)
Target Value: 0 - 4 dKH
Carbonate hardness (KH) is determined by the concentration of carbonates and bicarbonates, which provide water with essential buffering capacity. These compounds bind to acids as they appear and neutralize them, thus preventing the pH from becoming more acidic. Carbonate hardness is the main contributor to alkalinity (a parameter used more for reef keeping), so the terms are often used interchangeably.
TOO MUCH
Carbonates and bicarbonates will lead to higher pH and reduce the effectiveness of acid buffers. Plus, they will essentially soak up carbon dioxide, binding to the molecules in a way that prevents them from being used by plants. Elevated KH can also cause excessive abiotic precipitation of calcium carbonate from solution, clogging heaters and pump impellers. Ways to decrease:
  • Dilution via water change (assuming new water has less or no KH)
  • Wait it out (minerals are constantly being depleted from aquariums)
TOO LITTLE
Natural acids are constantly being introduced into aquarium water, and if there is not enough KH to neutralize them, then the water will become vulnerable to dangerous swings in pH. However, if there are other pH buffers in place (a substrate of aqua soil, for instance), then the importance of KH is reduced or even eliminated altogether. Ways to increase:
  • Dose sodium bicarbonate or sodium carbonate
CALCIUM & MAGNESIUM (GH)
Target Value: 4 - 8 dGH
General hardness (GH) is comprised mostly of calcium and magnesium, plus trace amounts of other minerals. Calcium is vital for neurological functioning, and magnesium is an important co-enzyme for cells and is necessary for biological functions. In freshwater aquariums, calcium and magnesium deplete at roughly the same rate, so they are measured together as GH.
TOO MUCH
Too many minerals can cause excessive abiotic precipitation of calcium carbonate from solution, which can lead to clogged heaters and pump impellers. Ways to decrease:
  • Dilution via water change (assuming new water has lower GH)
  • Wait it out (minerals are constantly being depleted from aquariums)
TOO LITTLE
Low GH will have negative affects on the health and growth of animals. Ways to increase:
pH
Target Value: 6.2 - 6.8 pH
pH is a general environmental indicator that is the cumulative result of many different chemicals and compounds (especially KH). It is a measure of the acidity or basicity in water. Because water enters fish down to their very cells through osmosis, a change in pH of the water causes a change in pH of their blood. Regulating their internal pH takes time and energy, which is why fluctuations are dangerous to fish, even if the pH remains in the recommended range. Therefore, pH should be maintained constant to a 1/10 precision (e.g. constantly 6.7, not swinging between 6.6 and 6.8).
Ammonia | Aqua Lab Aquaria
TOO MUCH
High pH levels are usually the result of high KH, which comes with its own set of consequences. Aside from that, pH levels can be toxic if too high. Ways to decrease:
TOO LITTLE
It is usually a battle to keep pH levels low enough in a planted aquarium. But, pH levels too low can disrupt biochemical reactions. Ways to increase:
  • Dose alkaline buffer
  • Dose sodium bicarbonate or sodium carbonate
  • Decrease carbon dioxide injection or help it escape the water by splashing the surface
TEMPERATURE
Target Value: 76 - 80 F (24 - 27 C)
Temperature simply measures the heat within aquarium water.
Ammonia | Aqua Lab Aquaria
TOO MUCH
Heat stress occurs when high temperatures decrease the concentration of dissolved oxygen in water, inhibiting respiration. Heat stress can be fatal. Ways to decrease:
  • Blow fan across top of aquarium to facilitate evaporative cooling
  • Use a chilling device
TOO LITTLE
All metabolic processes slow down at lower temperatures. Ways to increase: