75-Gallon Fish Tank – Overview, Setup, Stocking Ideas

If you’ve only had 20-30-gallon tanks so far, upgrading to one more than double that can be scary.

And it should be. Setting up and maintaining a larger tank is more demanding than a smaller piece.

Fortunately, I’m here to help. Today, we’ll discuss 75-gallon tanks: how to set up one, layout and aquascaping ideas, and the main challenges to consider along the way.

So, let’s get it started.

75-Gallon Fish Tank Dimensions

The standard dimensions for a basic, rectangular 75-gallon tank are 48x18x21 inches. Naturally, not all tanks are made equal.

Depending on your vision, these values can change dramatically based on the tank’s shape and depth.

If you’ve never owned a 75-gallon setup before, I recommend sticking to the plain rectangular version. Cylinders, pentagons, hexagons, and other more exotic shapes are more fitting for more experienced individuals.

The tank’s shape will also influence the overall aquatic layout; a rectangular piece is easier to decorate and set up, given that most tanks are rectangular.

75-Gallon Fish Tank Stand

Go for metal. I agree that wooden stands are more eye-catching, but a full 75-gallon piece can weigh in excess of 800 lbs.

You can’t afford to play with such weight, especially when your fish’s lives are on the line.

Not to mention, a 75-gallon tank spilling over or falling and breaking can create quite an environmental hazard. The ideal metal stand should be strong and slightly larger than the tank’s overall size.

A good base is also necessary to prevent tip-overs or imbalance issues over time.

Also, consider getting a stand that’s easy to move in case you plan on relocating the tank. If you can’t find a tank stand to meet all these criteria, I recommend getting a custom-built piece.

The investment will all be worth it in the end.

How Much Does a 75-Gallon Fish Tank Weigh?

The standard empty 75-gallon tank weighs around 140 lbs, but this can vary based on the materials, the tank’s thickness, etc.

When filled, the tank can skyrocket to 850 lbs or more, depending on the number of fish you have, how much water you add, and the different decorative elements present.

Expect the tank to weigh much more if you add reef structures and corals, large volcanic rocks, or other heavy aquatic decorations.

As a side note, don’t overburden the tank. The tank’s bed can actually crack due to the massive weight, at which point the tank can become unusable.

Avoid sharp or unstable rocks or tank decorations that can scratch, crack, or even break the walls.

Most importantly, keep in mind that some aquatic fish tank rocks are harder and heavier than others. Volcanic rock, for instance, is a lot heavier than limestone.

How Much Does a 75-Gallon Fish Tank Cost?

A standard 75-gallon glass tank should cost you around $200, depending on where you’re getting it.

An acrylic piece can go triple that, reaching $650-700. The tank’s price is also influenced by a variety of factors like shape, wall thickness, and other aspects.

Generally, pre-built 75-gallon tanks are quite difficult to find, causing many aquarists to go for custom-built pieces instead.

This way, you can select the material, the tank’s exact measurements and shape, and any other metric, depending on your goals and the depositing space available.

It will clearly cost you more, as most pre-build 75-gallon tanks can reach close to $1,000 per piece, but it’s worth it. Especially if you’re in the aquarium business for the long haul.

How Many Fish for a 75-Gallon Tank?

This is nearly impossible to answer the question. That’s because it all depends on the fish you’re housing.

If you’re going all out on small livebearers like guppies, platies, and swordtails, expect to fit dozens of them in the environment.

One guppy requires approximately 2 gallons of water, so you can have at least 30 of them in your 75-gallon piece.

On the flip side, you can rely on a 75-gallon tank to house one lionfish, as these creatures are in high demand of swimming space.

The tank’s layout also makes a massive difference in this sense. Some fish demand specific environmental settings, including live plants, rocks, reef structures, and other decorations that take up space.

The tank’s equipment, like a heater, filter, or air pump, can also occupy valuable water space, so you should account for that as well.

75-Gallon Tank Stocking Ideas

There are numerous potential stocking ideas to consider, especially with a tank this size.

Here are 3 of my favorites:

Paludarium

Nothing beats the paludarium in terms of aesthetics and visual impact. For the uninitiated, the paludarium is a mixed setup, combining land and aquatic environments for a well-rounded aquascaping experience.

The paludarium offers a lot of potential in terms of sculpting the available environment. You can include apple snails, tree frogs, and a series of nano fish to populate the water, like tetras or harlequins.

The vegetation also offers a lot of potentials, as you can use anubias, peacock moss, and tree logs for a jungle-like look.

Paludariums are easy to keep, as the actual aquatic setting is smaller, so it’s easier to maintain.

Community Tank

Community tanks are more difficult to set up and care for due to holding multiple fish species, each with its own requirements.

Fortunately, your 75-gallon tank has a lot of space to play with, allowing you to accommodate all fish easier.

Such a system allows you to add rocks and caves and ensure sufficient open swimming space to accommodate the different fish varieties with different requirements.

Just make sure that the fish are all compatible in terms of overall tank conditions and layout.

Carnivorous Setups

Many people get 75-gallon tanks to house single large predators like the flowerhorn cichlid, the jaguar cichlid, the redtail shark, or groups of aggressive and territorial cichlids.

The tank’s extra size is great, as it allows you to personalize the setup according to your fish’s requirements.

How to Set Up a 75-Gallon Fish Tank?

The actual setup process isn’t that much different than any other tank. The only difference is in the magnitude of the process since you’re dealing with a lot more space.

Consider the following steps:

Assemble and Clean

Prepare the tank’s stand, make sure it’s stable and safe, and bring out the tank. Clean the tank inside and outside to eliminate dust or any dirt coming from the package.

Check the tank for any cracks or manufacturing imperfections that could jeopardize the piece’s integrity.

Mount the tank in its place, check its stability, and set up the rest of the equipment.

Prepare the filter, the heater, the air pump, the lights, and whatever else piece of equipment you might have.

Decorate the Tank

Add the substrate and clean it with a water hose to remove dust and dirt. When placing the substrate, always place the finest-grained one first and then add the larger one, including the rocks.

I mention this because many people use a mix of sand and gravel, in which case sand should cover the tank’s bed, and the gravel should go on top.

After vacuuming the substrate to eliminate any unnecessary dirt and debris, you can fill the tank with water. Always do so after placing all of the tank decorations, and only use dechlorinated water.

The chlorine in the tank water is poison for your fish and invertebrates and can linger in the tank for quite a while until the filtration system eliminates it.

Now you can add and anchor the live plants, making sure that they won’t budge.

I’ve already written a more comprehensive plant-related article, teaching various anchoring techniques based on your substrate type.

Check that one for additional support.

Cycle the Tank

The cycling process is vital to ensure the system’s stability and self-sustainability.

The goal is to create a microcosm of nitrifying and denitrifying bacteria that would turn ammonia and nitrites into nitrates and nitrogen gas.

These bacterial colonies preserve the system’s stability, replicating the natural processes that take place in an open aquatic system.

The cycling process is pretty straightforward and requires the following steps:

• Add an ammonia source – You can either use several pinches of fish food or even rely on pure ammonia. The idea is to have ammonia levels below 5 ppm and nitrates below 20 ppm. Have a water tester kit to monitor those values daily.
• Add a source of bacteria – You can purchase liquid bacteria from any fish shop designed specifically to aid in the cycling process. You don’t absolutely need them since these bacteria will form naturally in the tank anyway. But they will drastically reduce the timeframe necessary to complete the cycling process.
• Water changes – Water changes are necessary daily or every 1-3 days, depending on how fast ammonia is rising. Perform a 20-25% water change whenever ammonia levels jump past the 5-ppm threshold. Water changes are also necessary whenever the water’s pH goes below 7.0.
• Maintenance surveillance – All you have to do now is wait. The goal is to see nitrates going up and ammonia levels going down. The cycling process should last approximately 4 weeks or less, given that everything goes according to plan. You know that the cycle is complete when ammonia and nitrites read 0 and nitrates remain between 10 and 20 ppm. Monitor the environment for 48 more hours to ensure the system is stable.

It is now safe to add the fish.

Adding the Fish

This is a step-based process in its own right because you want to prevent your fish from experiencing relocation stress or shock.

The main concern is the temperature difference between their temporary aquarium and the main one.

So, you should allow your fish the time to adapt to their new setup gradually for minimal risk of shock.

To complete the acclimation process safely, consider the following steps:

• Place your fish into a polybag containing water from their old tank/container
• Place the polybag into the newly cycled tank, careful not to spill any of the polybag water into the tank
• Keep the bag semi-submersed for approximately 20-30 minutes until the temperature in the bag matches that in the tank
• Use a fishnet to collect the fish from the bag and transport them carefully into the tank

Friendly reminder, do not empty the bag into the tank. The bag contains stale water, most likely infested with parasites and bacteria that you do not want in the new tank.

Is it OK to Buy a Used 75-Gallon Fish Tank?

I guess it depends on how you define ‘OK.’ I would advise against getting a used tank mainly for integrity reasons.

You don’t know how much the tank has been used and how sturdy it is. It might look fine on the outside, then experience structural issues when you least expect it.

Sure, second-hand fish tanks are cheaper, but is it worth the risk? I recommend going for a new one, especially since a high-grade glass tank can last up to 25 years or more. Given a proper maintenance, of course.

Conclusion

A 75-gallon tank is undoubtedly a spicy investment, from the tank itself to the fish and equipment necessary along the way.

You may be intimidated by the notion of acquiring one, especially if this is the largest tank you’ve ever had.

Fortunately, as you can see, preparing and maintaining a 75-gallon setup isn’t that much different than a smaller piece.

It all comes down to scale. Do your homework, and you should get the hang of it fairly fast.