Vertical vs. Horizontal Aquarium Heaters: Which is Better?

Choosing the right heater for your aquarium is paramount to the survival and well being of your fish. Unless you want to heat up your entire house all through the year you need to get a high quality attachable heater. While some heaters are specifically made to be placed horizontally or vertically, most models and brands allow for both, so the choice is yours.

The question is; when it comes to vertical vs. horizontal aquarium heaters: which is better? Generally speaking, placing your heater in a horizontal position instead of vertically in the tank is the best option.

Heater PlacementHorizontalVertical
Overall Better PlacementHorizontal placement is the overall better position to secure your aquarium heater, but it isn’t supported by all models. 
Heat FlowExcellent in narrow and tall tanks. Heat also rises to the top, which allows for great flow.Great when placed next to the filter intake. Not recommended for long tanks unless you get a second heater.
VisibilityVery visible and may be ugly to look at.More concealed with the natural edges of the tank and masked when placed next to the filter intake.
DurabilityYour fish aren’t likely going to break the heater, but it is a possibility. Since most fish swim more towards the bottom this could potentially pose a problem.Depends on the model and casing as well as where your fish tend to swim, but on average, when placed vertically, aquarium heaters last longer.
SafetyGenerally more safe.Could be dangerous if placed in water incorrectly.
CostDepends on the model.Depends on the model, but if you have a long tank and decide to have a vertically placed heater, you should get two heaters, which means double the cost.
Energy ConsumptionConsumes less energy as heat naturally rises.Will likely consume more energy to heat the entire tank.
MiscellaneousYou won’t have to remove the heater when doing a water change as the heater is placed low towards the bottom.You’ll likely have to turn off or remove the heater when doing a water change to avoid damages.

While a horizontally placed heater is better in most cases, there are some tanks, situations, and heater types where this isn’t necessarily the case. Read below to find out what will work best for your aquarium and specific needs.

Fish Tank Heater Placement for Optimal Heat Flow

Obviously, the most important thing you need to consider when buying a heater and where to place it in your aquarium is heat flow. You want to place your aquarium heater where it will allow the heat to flow throughout the tank so that your fish are warm enough no matter where it swims.

In general:

  • Horizontal Placed Heaters: work best in most tanks
  • Vertical Placed Heaters: work best when placed next to the filter intake

Your tank size actually has a lot to do with where and how you place your water heater. In all honesty, with a small tank, it almost doesn’t matter how you place the heater. It’s when you start to expand into more mid-sized and large tanks that you have to consider heat flow. In any case, a horizontal placement is going to prove more energy efficient and accurate in terms of heat dispersion.

Horizontal Placement is Ideal for Most Tanks

For the most aquariums, you want to place your heater horizontally at the base of the tank.

Here’s why:

  • Heat rises naturally, which is why most brands recommend placing the heater at the bottom.
  • Not to mention, with a horizontal position, you are going to get a nice even dispersion of heat throughout the tank, keeping all areas warm.
  • This is also great in terms of cost and the amount of energy needed to heat up the water, which we will get to in a bit.

Using the provided suction cups secure the heater in a straight horizontal position at the bottom of your aquarium but make sure it is not touching the bottom. You want to leave a good inch or two.

Vertical Placement Near Filter or Intake

On the other hand, vertical heaters can let you down when it comes to specifically covering the entire tank.

Most heaters can be used in both positions, and even at an angle, but no matter the position, you will be using suctions cups to attach the heater to the tank.

Ideally, you want to place a vertical heater right next to the filter intake, but make sure no parts are touching. This will allow for the flow of the water within the tank to carry the heat around the tank.

There are a few problems with installing your aquarium heater in a vertical position. First of all, the current isn’t exactly optimal or very fast inside the aquarium. In other words, it’s going to take a long time for the heat to spread throughout the tank.

What you could do is place a second vertical heater at the opposite end of the aquarium, which should even out the heat diversion. Of course, this means you will have to double your initial cost for buying a heater.

Visibility of Your Aquarium Heater

Fish are beautiful, but you already know that so you want to limit what you place in your tank to let the beauty of your little pets shine through… We get that.

On the other hand, you also have to make sure your fish are warm enough to stay alive and healthy. This is where the endless battle between form and function comes into play.

Heaters aren’t exactly pretty, so you may want to limit how visible they are. If placed horizontally, there isn’t much you can do to hide the fact that there is a long rod in the middle of the tank with a small indicator light on it and a wire making its way out of the aquarium.

It’s an eyesore, and there is no way around it. No matter how many decorative plants and plastic castles you put in there, you and everyone else, are going to be looking at the heater.

Not to mention, another cosmetic problem, but most heaters come with pre-selected suction cup colors. So if you have a black drop behind your tank and you get white, grey, or some other color of suction up, you’re going to have even more eyes fixated on the heater.

Vertically placed heaters are noticeably more humble and aesthetically pleasing.  The corners of the tank, whether curved or sharp-angled, almost skew your vision making anything in that area almost blend and in some cases disappear, like half of whatever object is placed between two pieces of glass looks like it has been cut.

Placed vertically, the heater becomes a side piece and not a main focal point. Not to mention, when placed next to the filter, which you should do anyway, it blends as another mechanical part of the tank that just has to be there, and everyone sort of accepts that whereas horizontally it’s screaming to be looked at.

How Placement Impacts Aquarium Heaters Wearing Out

Durability is more important than you may think. If your heater malfunctions and you don’t find out about it until it’s too late… well, let’s just hope it is not wintertime.

You want to get durable heaters for your fish tank, no matter if you plan on placing it in a vertical or horizontal position. This largely depends on the brand you decide to buy, which we will get into at the end, but placement will impact how long your heater lasts.

Most fish tend to swim near the bottom of the aquarium, and they don’t tend to hand out around the edges. Now this may not be true for your little fellas, so you need to observe them and objectively asses on average where the fish swim and hang around the most.

In any case, if your fish swim more towards the bottom, then they are likely going to crash or bump into the horizontally placed heater.

This may seem trivial, but some fish can be rough and eventually crack or cause damage to the heater, which can either kill the fish or make the heater malfunction, which will also kill your fish… just slower. If your tank is mostly guppies, this probably isn’t a major concern, as they’re very small, but plenty of larger fish have enough force behind them to cause damage over time.

Vertically placed heaters are more likely to last longer, not because they are made of some other material (if anything it’s the same heater), but because fish don’t swim as much near the edges as they do near the bottom.

In any case, look for a high quality heater with a case. If you don’t find one, you can always buy casing separately.

Safety: Get to Know Your Manual

Now you may be thinking, how can a small hater in a fish aquarium not be safe? Well, anytime you have electricity, heat, and water involved, you better read the instructions manual.

Some brands specifically build heaters to be placed horizontally or vertically. Others recommend one over the other, and some like Fluval E will consider your warranty annul if the heater is placed horizontally instead of vertically.

While heaters are generally waterproof and fully submersible, there are some that need to be placed slightly above the water at certain points. Some models and brands that specifically make vertical heaters have a line or gauge from which you can’t immerse the heater any further into the water; otherwise you risk damaging the heater, or worse, harming your fish.

Heaters that can be placed horizontally don’t have this problem since the heater is fully submerged anyway.

No matter which heater you decide to use in your aquarium, make sure you double check the manual for placement recommendations.

The Cost of Vertical vs Horizontal Aquarium Heaters

With any product cost is a major consideration and deciding point. Of course, when it comes to the safety and well being of something you love it is worth going a bit over your budget.

We will go over specific products and their costs at the end of the article but for now, consider this:

  • Unless specifically written in the heater’s manual, most heaters can either be placed horizontally or vertically. Based on your tank size and shape your placement may differ. So the cost of equipment should not be any different.
  • With a horizontal placement, you can pretty much cover the entire tank since there are also very long heaters, and heat naturally rises even in water. With vertical placement, you may have to get a second one to make sure your heat flow is effectively spread throughout the tank. This means you would essentially have to pay double.

But! Keep in mind one thing, if you have a really large tank, one heater may require an immense amount of energy to supply enough heat to the entire system rendering it ineffective or extremely energy consuming, making it cheaper to operate two heaters working at normal capacity.

Which brings us to…

Energy Consumption: Vertical Heaters vs Horizontal Heaters

Energy consumption has a lot to do with the costs associated with your aquarium heater.  How much energy your heater requires will relate directly to heat flow and tank size.

Of course, the larger tank you have, the more energy it will take for one heater to cover everything.

As a general rule of thumb, you need between 4W to 5W per every gallon of water in the aquarium.

10 gallon tank40W – 50W
20 gallon tank80 W – 100W
50 gallon tank200W – 250W
100 gallon tank400W – 500W

Most heaters don’t go up to 500W. Instead, for a 50 gallon tank you can buy two 100W heaters or two 300W heaters for a 150 gallon tank and place them vertically at opposite ends of the tank.

Your heaters aren’t going to be working all the time. Once the water in your aquarium reaches the temperature that you set the heater to, it will turn off until it is time to turn back on again.

Your heater will come with a twistable dial that will allow you to manually adjust the temperature you want it to work at. The amount you select will depend on the kind of fish you have.

  • Temperate fish: These fish are comfortable in water at around 79 degrees Fahrenheit or 26 degrees Celsius.
  • Tropical fish: These fish enjoy water up to 82 degrees Fahrenheit or around 28 degrees Celsius.

If you have two heaters in the tank, the water will reach the desired heat sooner, thus turning off your vertical heaters. This will save you more energy than if you had a big tank and a single horizontal heater working at full capacity all the time just barely getting the job done.

In terms of the heater size, the old bigger is better adage holds up. You want to be safe when it comes to this sort of thing, so it’s always better to have a bigger, stronger heater that can go upwards of 300W and heat up the tank in less time than to go with multiple heaters at lower powers.

One final thing you should consider before making your mind up about efficiency. It is not entirely uncommon for a heater to malfunction or just stop working.

If that is the case, you want a backup heater that will carry the burden. Sure it will work at double the capacity and concentrate heat in one location, but it’s better than having no heaters at all.

So double placed vertical heaters are better when it comes to energy efficiency, and they also provide a fail safe if one heater stops working.

Cleaning the Tank: Horizontally Placed Aquarium Heaters are Better

One more thing you need to consider before we get into the best heaters on the market.

It is recommended that you drain half or at least a third of your aquarium water every month or so. This allows for new fresh water to come in but still maintains a healthy level of the bacteria and micro-environment your fish have grown used to.

Unfortunately, your heater can’t work while it is outside of the water… well, it can but not for long not functionally at least. Which is one reason why it’s recommended you place your heater in the filled aquarium for a few hours before you turn it on.

If you place your heater vertically, you have to turn it off before draining the water. On the other hand a horizontal heater is so deep you won’t have to shut it off making it all the more convenient.

If having to deal with your heaters every time you perform tank maintenance will bother you, then stick with a horizontal heater.

The Best Aquarium Heaters

No matter which way you decide to place your heater or heaters, you are going to want to buy a high quality aquarium heater to keep your fish at a healthy temperature. One of the most devasting things that can happen to a fish tank is a faulty heater, so don’t skimp here!

Here are two of the best aquarium heaters around:

  1. The EHEIM Jager heater: This is among the best on the market for home aquariums. It comes in multiple powers and lengths making it ideal for horizontal placement. The great thing about EHEIM is that you can place the heater vertically or horizontally as necessary.
  2. The Hydor In-Line External Heater: This is another great heater with one tiny flaw. It can only be placed vertically. Of course, if that’s what you’re going for in the first place well then you’re good to go!

Make sure you check the manufacturer’s recommendations before positioning your heater; otherwise, you are best off with a horizontally placed heater especially for the average sized home aquarium. Then again if you are looking for something at a larger scale and are willing to pay an extra buck then vertical placement isn’t a bad option either. Whichever position you chose make sure to take good care of your fish and keep them nice and warm.