Temperature – The Planted Aquarium Water Parameters

Weekly water parameters tests from the beginning weeks to months of your planted aquarium are critical to making sure that your parameters are in check, don’t let others say otherwise. The way co-hobbyists talk about good water parameters can be confusing at times. Add that to the fact that you may have different water sources and parameters due to your differing location/city, and you may not be able to replicate what works for him/her. That is why every planted aquarium is unique, and you have to find the balance of what you’ve got in hand.

Knowing what makes ‘good water’ for your planted aquarium is critical for maintaining a healthy environment for your fish and plants. It will help us understand the intricacies of a planted aquarium and will arm you with valuable insights on what to do if you notice any problems. Knowing good water parameters even helped me think outside the box, formulate theories, and tested it to see what works and what doesn’t, which I will explain later below.

The planted aquarium water parameters can be further broken down into categories, namely:

We will not over-complicate this. Temperature is simply just the measure of how much heat is in the water, hot or cold. But too big fluctuating temperatures will have bad effects on your faunas and plants in our planted aquarium.

Avoid placing the tank near heating vents, fireplaces, radiators, and air conditioning units exhaust because those can drastically change the water temperature in your tank. You would be amazed at how quickly the temperature inside your aquarium can change. But a planted aquarium in an air-conditioned or heated (using a heater) room will help you maintain your planted aquariums temperatures in countries with scorching hot summers and coldest winters, respectively.

Properly drip acclimating your newly bought fish involves temperature acclimatization too, which was discussed thoroughly as part of this article, wherein you don’t just pour your newly bought fish along with the pet shop water directly to your tank as the water parameters, and temperature from the pet shop may be very different compared to your tank.

Cool to the Touch Water

Most commercial aquarium plants prefer cool waters, plus the capacity of water to hold dissolved oxygen increases as the temperature decreases. Cool waters mean more dissolved oxygen. All metabolic processes slow down in cooler water too, less chance of plants melting, slow and controlled growth, less need to eat for faunas, means fewer wastes. Plus, plants uptake of nutrients and CO2 are better with cooler waters. More oxygen means happy and very efficient beneficial bacteria action too.

So we always recommend cool to the touch water range or middle ground (from 24 to 28 °C) temperatures for our planted aquariums. So what is cool to the touch water temperature? Well, it depends on your perception of warm or cool water, which also depends on what weather extremes you used to. For me, water below 29 °C feels cool to me already.

Fish that prefer warmer waters such as Cardinal Tetras or Discus can actually live in cooler waters. They may not or will not breed at all though. Most of these fish were actually bred in captivity for many generations and already adapted to cooler waters. Shrimps, though, require maintaining temperatures in the 19-23 °C range (66-72 °F).

Warm Waters

As I said earlier, water’s capacity to hold dissolved oxygen increases as the temperature decreases, which means warmer waters can hold less dissolved oxygen even if you are providing water surface agitation. You may not be able to breed fish that are known to breed in certain warmer temperatures, but that alone is enough reason (cool water = more oxygen) for me to choose middle ground cooler waters.

Plus, all metabolic processes accelerate in warmer waters. More chances of certain plant species melting, fast growth, and more need to eat for faunas mean more waste.

What Should be the Best Temperature Levels for Our Planted Aquariums?

The following table provides acceptable water parameter ranges for different types of freshwater aquariums and tropical ponds. Please take note that these are just general guidelines for maintaining each specific type of aquariums or ponds. Some species of fish, plants, and invertebrates may have more specific requirements. Please research the specific faunas needs first (you can scroll the table horizontally on mobile devices).

Please also take note that I already included the other critical water parameters values or ranges. For this part of the article, please check the Temperature row. Please also note that we recommend not exceeding 30 °C for our planted aquariums. This is a common problem here in the Philippines during the scorching heat in our summer months (March to May), plants melting, moss browning, faunas dying one by one due to the hot ambient temperatures even exceeding + 40 °C.

Too Warm?

Heat stress happens when high temperatures decrease the concentration of dissolved oxygen in water, hindering our faunas’ respiration. Heat stress can be lethal, and I lost some of my beloved faunas during those times. Water temperatures greater than 35 degrees Celsius will not hold oxygen anymore and can also kill your good bacteria, you lose your biological filtration causing Ammonia spikes.

Ways to Decrease

• Evaporative Cooling – blow an electric fan or CPU fans (like I did) directed to the water surface to facilitate evaporative cooling. The only problem with this is if the room where your tank is located is sealed, no windows for ventilation, your fan is still blowing hot air and may not help at all to decrease the water temperature.

Ways to Increase

While we don’t have winters in the Philippines, the lowest I can get in my outdoor terrace tank was 21 °C (this was my happiest). But homes in other places/countries even have winter storms, while the most common device is recommended to make the water temperature consistent and not to dip below uncomfortable levels for your faunas and plants is using an aquarium heater appropriate for the size of your tank, what if you have blackouts during winter storms? How can you keep yourself warm and your planted aquarium?

Normal Winters (no Blackouts)

• Use an Aquarium Heater – you must determine the right size/wattage aquarium heater for your planted aquarium, which depends on the water volume of your tank, the average ambient temperature of the room where your tank is located, and your desired final water temperature of the tank.

Invest in quality heaters, not on cheap ones that may pose durability issues, electrocution, or turn your aquarium into a fish soup when they malfunction (stays on the ‘on’ position). For added peace of mind, you can also invest in a temperature controller which will act as an overlord to cut the power into your heater/s when it gets warmer than your upper temp settings and bring the power again when it gets colder than your lower temp settings.

Please find the table guide below in determining the right size aquarium heater for your planted aquarium (you can scroll the table horizontally on mobile devices).

For example:

• Average Room Temperature – 18 degrees Celsius
• Your Target Water Temperature – 27 degrees Celsius
• Get the Difference (Heating Required °C) – (27-18=9) 9 degrees Celsius.
• Tank Size: 35 Gallons
• Heater Size Needed Should be = 150 watts.

It is important to note in larger tanks (75 gallons and up), two heaters may be required to ensure even heating distribution across the whole tank. This also puts less strain on the heaters. The heaters should be put on both ends of the tank, plus if one heater fails, the temperature will not dive drastically until you can get a replacement. You should also have good water circulation across the whole tank by using wavemakers or water pumps.

• Room Heaters, Radiators, or Fireplace – if you have situated your planted aquarium in a room where you have a room heater, radiator, or fireplace for cold winters (stock up on firewood), you can certainly utilize it to stabilize your water temperature and not let the temp dip below uncomfortable levels for your faunas and plants. This should be part of the plan at the beginning when deciding to keep a planted aquarium at your home, and you have extreme weather like winters.

Winter Storms (with Blackouts)

Your planted aquariums may be at risk when the power goes out during winter storms. We had listed a few simple precautions below and some emergency supplies that you can stock up to protect your faunas and plants from frigid water temperatures and lack of filtration or aeration during a blackout.

Here are some general tips to keep your planted aquarium warm in cold winters with blackouts:

• To minimize the build-up of wastes and degradation of your water quality, reduce the amount you feed on your faunas until the electricity comes back. One can go as far as feeding every 2-3 days since all metabolic processes slow down during cold weather.
• If possible, move your tank away from windows to keep drafts to a minimum. Don’t put your tank near windows in the first place, as we recommended in the “Where to Place Your Planted Aquarium at Home” article.
• As part of the planning, locate your tank in a room where you have a fireplace but not near it. This is also the room where your family will likely close off and retreat to in case of a blackout during winter storms.
• During a blackout, cover and close all windows in the room with blankets, sheets, and employ a draft-stopper or towel under the door.

Be Prepared Always

While a UPS can provide hours of power to your essential equipment for your planted aquarium during a blackout on a winter storm, it is still ideal to stock up on the rest of the emergency supplies because you’ll never know how long you are out of power.

How to Test?

There are 3 types of Aquarium Thermometers known in the hobby. I personally used the Standing Thermometer from Resun (Analog one – Mercury Type). For my needs, it is accurate enough and cheap (no batteries needed), better than some cheap digital thermometers, unless it is the lab grade digital thermometers, which are more costly and have alert features. It had served me for 9 months plus, and then it breaks. I am getting another one again.

There are also Temperature Controller Thermostats in the market wherein you can set the highest temperature that will make your aquarium fan turn on to cool the water temperature and turn it off when it reaches the temperature you set after cooling.

Update January 2022: I started to use a thermostat for my planted aquarium but I am not using the feature, just for the temperature measurements. I replaced my in-tank thermometer to free up equipment inside my tank plus the suction cup is not working anymore.

Stressing This Out Again

I want to stress again. Every planted aquarium is unique. What worked for others may or may not work for you. We all have a differing degree of planting, tank sizes, water parameters, water sources, stocking, maintenance schedules, lighting (intensity and spectrum), injecting co2 or not, filtration, aeration, substrates, even external factors like extreme weather conditions and ambient temperatures, etc. it is up for the hobbyist to find the balance of all these factors.

You can also ask for help from others who are willing to help and have the experience. A sensible co-hobbyist will ask some questions first before jumping to conclusions (even if he had the same symptoms before) like what is your water parameters, how old is your tank, did you perform any tank cycling, or do you even know what tank cycling is, what did you changed before the problem happens, what is the size of your tank, filtration used, the substrate used, how is your stocking, your feeding schedule, and maintenance, to name a few.

From your answers, he may be able to create a hypothesis and test it. He may ask additional questions to prove his theory further until you both reach a conclusion and resolve the problem.

Conclusion

Temperature is just the measure of how much heat is in our water. But too big fluctuating temperatures will have bad effects on your faunas and plants in our planted aquarium.

We also discussed water’s capacity to hold dissolved oxygen, depending on the temperature of the water. Cool water means more dissolved oxygen holding capacity, while warm water has less dissolved oxygen. We also provided the ideal water temperature ranges for different freshwater planted aquariums and ponds.

We also covered the science of how fish and plants survive freezing winters in the wild. That fish have omega-3 fatty acids in them that lower their freezing point and let them have more resistance to icy weather. Lakes and rivers do not freeze completely due to the elasticity property of the water.

Consequently, we touched on how to stabilize your tank’s water temperature during the scorching hot summers and freezing winters in other regions of the world. Finally, we also provided the essential emergency supplies that will help you keep your planted aquarium warm during winter blackouts.