Richard bray

Water Temperature
The water in your fish tank should not fluctuate more than 3° per day in either direction. Large fluctuations can stress your fish, which can lead to lower activity and disease.
Aim for a temperature that fits your fish and your plants, and try to maintain that temperature throughout the year. This is easier in an indoor system, but it’s possible in some outdoor systems in certain climates.
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It is always easier to heat water than it is to cool it down, so try to design your system around warm-weather thresholds rather than cool-weather thresholds. A hoophouse can help maintain warmer air temperatures for plants during winter months. Shade cloth or canopies can prevent the water temperature from climbing during the summer.
Record the water temperature at the same time every day. Gradual declines are fine as long as they remain within the healthy range for the fish. A log of daily temperatures will help you determine how your system responds to weather patterns, which will help you plan in the future.
Water Testing
You should try to test your water once per week. A basic freshwater aquarium test should show the ammonia levels of your water, and a hydroponic water test will check basic nutrients.
Keep a log of your test results each week so you can compare temperature fluctuations to nutrient fluctuations. You should also record any activity that may impact results, like a water change or harvesting large amounts of plants or fish.
Plants are fairly tolerant of nutrient fluctuations, so you want to avoid amending the water with a specific nutrient unless the plants show signs of deficiency. Wait to see if the pH, temperature, or fish feed may be causing nutrient problems and make adjustments there before adding new chemicals to your system.
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pH Testing
The pH levels of your system will determine how much of each nutrient is available to your plants. Too low or too high, and certain nutrients become deficient or toxic very quickly.
The balance between the ideal pH for plants and the ideal pH for fish can be difficult to maintain. Nitrification lowers pH, while denitrification raises it. Adding new water can raise or lower pH, and sometimes a pH imbalance seems to come from nowhere.
Plants and fish can tolerate pH values outside of their ideal range as long as they happen gradually. If your pH is too low or too high, you can use an amendment to raise or lower your pH. However, you will want to do this slowly, and try to adjust the value by no more than .3 points per day.
Keep a log of the pH each time you test. This data, along with your temperature and nutrient logs, can help you predict how your system will react to certain situations in the future.