Temperature – The Planted Aquarium Water Parameters
Every healthy ecosystem requires a balanced environment, including the environment we lived in. Just like we humans and land animals cannot survive breathing polluted air or drinking contaminated water, aquatic life (faunas and plants) will have a difficult time living in sub-optimal water. Of all the balanced factors that go into a successful planted aquarium – the filtration, lighting, CO2 injection, fertilization, substrate – I would insist that the quality of the water used in our planted aquariums may be the most important. In this article, we will be discussing the environmental indicators Temperature part of the planted aquarium water parameters.
Table of Contents
Cool to the Touch Water
Best Temperature Levels for Our Planted Aquariums
Ways to Decrease
Ways to Increase
Normal Winters (No Blackouts)
Winter Storms (With Blackouts)
Essential Emergency Supplies
Be Prepared Always
How to Test?
Stressing This Out Again
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:
pH is the measure of the acidity and basicity of your water. The range goes from 0 to 14, with 7 as neutral. pH lower than 7 indicate acidity, and pH greater than 7 indicate basic or alkaline water. Like the Richter scale used to measure earthquakes, the pH scale is logarithmic, so a pH of 5.5 is ten times more acidic than a pH of 6.5.
We will not over-complicate this. Temperature is 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.
Carbon dioxide is naturally produced in our planted aquariums, even if you are not injecting CO2. When beneficial bacteria break down the wastes in our tank, and when faunas respire, CO2 is produced. While carbon dioxide accumulates during lights off, it will quickly be depleted by your plants at the start of lights on.
If you are sourcing your aquarium water from a commercial water system (tap water), water should be treated to ensure it is safe for human consumption. The water is cleaned and filtered, then add chemicals to prevent anything harmful from developing in the water while traversing the pipes leading to our homes.
TDS is the measure of all dissolved organic and inorganic solid substances in your water. However, the test of this water parameter doesn’t say what comprises your TDS. It measures the total of all molecular, ionized, and any microscopic substances in our water that cannot be caught by your filtration.
After we discussed the pH part of determining good water parameters for our planted aquarium, we will now be discussing the Temperature part, what are its effects, what happens if you have too much or too low, what can you do if you have too much or too low, how to test it, etc. We will also provide the acceptable water parameter ranges for different types of freshwater planted aquariums near the end of these articles.
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.
Since I am in a tropical country, and my tank is in our terrace (completely shaded, no direct sunlight), I installed a couple of dual CPU fans (directed to the water surface) to maintain the water temperature (evaporative cooling) in the 24 to 25 range (evening) to 26 to 28 C range (10 am to midday until 3 pm). The Philippines have a tropical maritime climate, meaning the weather is generally hot and quite humid.
Average temperatures in the Philippines usually range between 21 °C (70 °F) and 32 °C (90 °F), with the average yearly temperature coming in at around 26.6 °C (79.9 °F). Temperatures can fluctuate between regions and depending on the season. However, generally, January is the coolest month, while May is the warmest.
Remember, your water temperature will follow the room’s ambient temperature depending on where you located your planted aquariums. Hence, we recommend including the weather extremes of your location in your plans to keep a planted aquarium. Some countries have scorching summers (+ 40 °C) and freezing winters (those are not good). But assuming you are using an air conditioning unit during hot summers and a room heater during freezing winters at your home, put your aquarium in that room, then you are all set.
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.
Cool to the Touch Water 26-27 C
26 degrees Celsius on a midday, in a terrace tank, in the Philippines, and it is summer
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).
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).
Alkalinity (Carbonate Hardness - KH)
General Hardness (GH)
Freshwater Community Planted
Freshwater Amazon Blackwater Biotope Planted
Lake Malawi African Cichlids (Scarcely Planted)
Freshwater Clearwater South American Biotope Planted
Tropical Pond Planted
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.
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.
Using an Electric Fan for Evaporative Cooling by Ian Paz Philippines
DIY CPU Fans for Evaporative Cooling by Jedz Florita Philippines
I managed to have 26-27 °C, blowing x4 strong CPU fans in my planted aquarium, even midday, last summer here in the Philippines. But that is because my tank is on the terrace, lots of ventilation and no direct sunlight. It can easily shoot to + 32 °C without my fans. I realized this is one of the benefits of an outside planted aquarium during the scorching summer heat in the Philippines, plenty of ventilation, and helped my fans blow fresh air into my aquarium.
- Airconditioned Room – planning and locating your planted aquarium in an air-conditioned room in your home will tremendously help you beat the scorching summer heat. Just provide proper room isolation/insulation to the outside world even if you are just using the air con at night when sleeping or certain hours of the day, preserve the cool temperature by always closing the door and windows.
A Planted Aquarium in an Airconditioned Room by Omar Krishnan Afuang Philippines
You might be wondering why we didn’t recommend an aquarium chiller? Well, you can certainly use one, and no one can stop you but unless you have the means to buy an air conditioning unit for the room where your aquarium is located, then buy an air conditioning unit.
An air conditioning unit benefits the owner/hobbyist, even the whole family, plus the plants and fish in one electric bill entry. An aquarium chiller only benefits the plants and fish. Plus, if your location is just too hot, the aquarium chiller will always compensate and will put a dent in your pocket concerning electrical bills. Additionally, we don’t really recommend an aquarium chiller for beginner hobbyists.
Preparing frozen water in Soda plastic bottles and dropping it into your tank just provides a short term effect (or no effect at all) for very large tanks, as well as putting chlorine-free ice cubes directly into your tank. It can work with small tanks longer, but your tank will still quickly align itself to the ambient temperature, melting the ice quickly, unstable results and ineffective, plus the hassle of preparing these ice every day and in your electrical bill (where do you think those ice you prepared come from?).
If you have freezing winters in your location, that is not good for the people living there without adequate protection, more so with your faunas and plants. While some aquarium plants can adapt in cold waters (even as low as 14-15 °C), such as Anacharis, Hornwort, Java Ferns, some fish prefer cold waters too, such as Goldfish, Barbs, Danios, and Minnows, to name a few but keeping your temperature stable and not dipping so low is paramount during the very cold weathers.
Goldfish, Koi’s, and other carp family members are desirable pond fish, in which they can withstand cold water temperatures as low as 10 °C.
Again, all metabolic processes slow down for your faunas, plants, and even us during cold weather. They don’t have to eat as much and move around. Heart rate is slowed down as well as breathing. You might be wondering how the fish and plants in the wild survive the frozen surface lakes and rivers during winters? What keeps them from freezing?
Most commercial aquarium fish were tank-bred for many generations already and did not come from the wild, so they may not have the same adaptability anymore to as low as 4 °C water under frozen lakes or rivers like fish caught in the wild. But the cells of most fish contain poly-unsaturated fatty acids called Omega-3s. These fatty acids prevent the fish from freezing by lowering their freezing point, making their cell membranes more elastic and providing them more resistance to cold temperatures.
Speaking of elasticity, H2O (water) is elastic too. Meaning when the outside temperatures dip below freezing, water first contracts and then expands as it begins to turn to ice. Ice floats because it is lighter than water. Meaning, the surface of the lake or river is the first part to freeze.
A body of water more than 1 meter deep will never completely freeze. Under this sheet of ice, fish can seek out warmer waters by swimming into deeper parts. The deeper the water, the denser it is, thus higher temperature compared to the surface. While the surface is frozen on lakes or rivers during winters, oxygen is trapped too under the ice.
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).
- 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.
5 Gallons/20 Liters
10 Gallons/40 Liters
20 Gallons/75 Liters
25 Gallons/100 Liters
40 Gallons/150 Liters
50 Gallons/200 Liters
65 Gallons/250 Liters
75 Gallons/300 Liters
5 Degrees C
9 Degrees F
10 Degrees C
18 Degrees F
15 Degrees C
27 Degrees F
Central Room Heating Radiator
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.
Essential Emergency Supplies to Stock-Up to Keep your Planted Aquariums Warm and Aerated During Power Outages
- A battery-powered aerator (and batteries too) – this is to keep your planted aquarium aerated/oxygenated during blackouts. Take note the part where it sucks air to your planted aquarium should be outside the Mylar blanket after you wrapped your aquarium with it for more effective oxygenation.
Battery Powered Aerator
- Firewood for your fireplace if there’s any
- Mylar Blankets – will help keep the heat in your planted aquarium during power outages in case you don’t have a fireplace. After you set up your battery-powered aerator, please turn it on and stickied your heat packs around your tank as explained below, wrap the Mylar blankets around your tank with the shiny side in, leave some looseness for your heat packs, use the duct tape to seal it around your tank.
- Heat Packs – heat packs can provide warming up to 72 hours, but 60 hours heat packs are the most commonly available. Take note these should not be used inside the tank. It should be stickied outside and around the tank using the duct tape (near the bottom – remember warm water goes up and cold water goes down). A good rule of thumb is to use two heat packs for every 25 gallons of tank volume at a time. So if you have a 100 gallons tank, you need 8 heat packs around your tank’s outside glass for every 60 hours when you are still out of power.
- Duct Tape – this will be used to stick your emergency supplies in place.
- UPS (Uninterruptible Power Supplies) – if you can invest in a UPS, it can keep your equipment running for several hours depending on how many equipments are plugged into it during a blackout. It will switch automatically and will provide you enough time to get home when you are outside. Obviously, two equipment that should be automatically switched to the backup power supply should be the heater and your filtration.
Uninterruptible Power Supply
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.
Dutch Style High Tech Aquascaped by Matt Mendez Philippines
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.
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.
Want to Explore More?
After choosing the ideal location of your aquarium at your home and the stand to be used, you have to determine your planted aquarium tank dimensions. You have to take measurements of the Length, Width, and Height (LxWxH) of the stand. Take into consideration where you will put your equipment, tools such as aquarium filter, aquascaping tools (straight tweezers, curved scissors), siphon, etc.
It is called the Fishless Method of Tank Cycling, which is self-explanatory. We will cycle our planted aquariums with no fish. We don’t have to be worried about any of our faunas anymore if they will survive the fish-in cycling we discussed in the previous article.
In its most common implementation, a Fluidized Bed filter is actually a 3 chambered sump separated by baffles. The big difference is that the biological media is held in suspension by a pumped water flow or bubbles from an air pump so that every particle of the media will have a large part of its surface area exposed to water flow and well aerated at any given time to home the beneficial bacteria that will filter the water off of Ammonia and Nitrites, as opposed to static media sump filters.
I hope you enjoyed this article. If you have additional questions or want to share your experiences with the Temperature Parameter in your planted aquarium, please leave a comment below. Next, we will be discussing the Dissolved Carbon Dioxide Parameter for our planted aquariums.