How to Set Up a Betta Hospital Tank (Step-by-Step Guide)

Your betta looks rough. Maybe you spotted fin rot creeping in, or he’s floating sideways like a tiny submarine that forgot how submarines work. Now you’re scrambling to figure out what a hospital tank even is, and whether you need one ASAP.

Here’s the deal: a hospital tank is basically your betta’s personal recovery room. It’s where sick fish go to heal without stressing out their tank mates or getting their main tank contaminated with heavy-duty medications.

Let’s get your fish ICU set up the right way.

Why Your Betta Needs a Hospital Tank (And When)

Think of a hospital tank like quarantine for your fish.

When your betta gets sick, keeping him in the main tank is like going to work with the flu and coughing on everyone. Not cool. Plus, most medications will nuke your carefully established beneficial bacteria, and some can harm plants or other fish.

A hospital tank gives your sick betta a clean, controlled space to recover. You’ll need one when dealing with fin rot, ich, fungal infections, swim bladder issues, or pretty much any condition requiring medication.

The best part? You can monitor your fish way better in a smaller, bare-bones setup. No plants blocking your view, no decorations for bacteria to hide behind—just you and your betta fighting the good fight.

How Big Should a Betta Hospital Tank Be?

Here’s where people get confused because everyone has different opinions.

The minimum is around 2.5 gallons, but 5 gallons is way better. Anything smaller than 2.5 gallons gets sketchy because water quality crashes faster than a coffee-deprived college student during finals week.

Some folks use 1-2 gallon containers for short-term medication treatments, especially when daily 100% water changes are required. That works if you’re religious about water changes, but it’s not a long-term solution.

Fish vets recommend 2.5-5 gallons for bettas specifically. The sweet spot is around 3-5 gallons—big enough to keep water stable, small enough to make medication dosing easy and affordable.

Also, bigger tanks mean less stress on your already-stressed fish. Nobody heals well when they’re cramped and uncomfortable.

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Essential Equipment (Keep It Simple)

A bare-bottom tank (no gravel, no substrate)

Here’s why bare-bottom wins: you can spot poop, medication residue, and any gross stuff way easier. Plus, when you’re doing daily water changes—which you will be—you don’t want to be vacuuming gravel every single time.

An adjustable heater

This is non-negotiable. Bettas need temperatures between 76-82°F normally, but some treatments require cranking it up to 80-85°F or dropping it down depending on what you’re fighting.

Get an adjustable heater, not a preset one. Fungal infections and bacterial infections respond differently to temperature changes, and you need that flexibility.

A reliable thermometer

Get a liquid crystal stick-on or a digital one. Just please, for the love of all that is holy, don’t guess the temperature. Fluctuating temps stress sick fish even more.

Gentle filtration (sponge filter or air stone)

Most hospital tanks skip filters altogether because medications require daily water changes anyway, and filters with carbon will literally remove the medication from the water.

If you do use a filter, go with a basic sponge filter. No carbon cartridges allowed. The goal is gentle water movement and oxygenation without creating a current that’ll exhaust your already-weak betta.

A simple air stone works too. Sick bettas sometimes struggle to reach the surface for air (they breathe from the surface using their labyrinth organ), so keeping oxygen levels high in the water helps.

One or two hiding spots

Don’t overcrowd the tank, but your betta needs at least one hiding spot. Sick fish feel vulnerable and hiding is how they cope with stress.

Use soft silk plants or smooth plastic decorations. Avoid anything with sharp edges—your betta’s fins are already compromised.

Some people use a floating betta log or a small terra cotta pot. Just make sure whatever you add can be easily cleaned and sterilized later.

A dark towel or background

Wrap a dark towel around the tank or use a black trash bag on the back and sides. This reduces stress by making your betta feel more secure and less exposed.

Plus, it blocks reflections that might stress him out. Bettas can get aggressive toward their own reflection, which is the last thing a sick fish needs.

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A lid

Bettas are jumpers, especially when stressed. Don’t give yours the chance to become a floor fish.

Setting Up Your Hospital Tank (Step-by-Step)

Fill the tank with fresh, dechlorinated water

Never use water straight from the tap—chlorine will kill your fish faster than whatever illness he’s fighting. Use a water conditioner (dechlorinator) following the instructions on the bottle.

Some people transfer water from the main tank to make the transition easier, but honestly? Fresh, treated water is usually better for a hospital setup.

Match the temperature to your main tank

Before adding your betta, get the hospital tank water to the same temperature as his main tank. Sudden temperature changes = stress = weakened immune system = slower recovery.

Let the heater run for a few hours and check with your thermometer before transferring your fish.

Add your filter or air stone

Get some gentle water movement going. If you’re using a sponge filter, you can steal one that’s already been running in your main tank to instantly add beneficial bacteria.

Just remember: any equipment coming back from the hospital tank to the main tank MUST be sterilized. We’re talking bleach solution, hot water, the works.

Add hiding spots and darken the tank

Toss in your silk plant or hide, then cover three sides of the tank with a dark towel or trash bag. Leave the front clear so you can monitor your fish.

Let everything run for 24 hours before adding your betta

This gives the heater time to stabilize and lets you make sure everything’s working correctly. A 24-hour wait also gives you time to observe the water temperature and make adjustments.

Emergency situations? You can skip this step, but definitely check temperature and dechlorinate properly.

Transfer your betta carefully

Use a cup or net to move your betta from the main tank to the hospital tank. Try to match water parameters as closely as possible—sudden changes in pH, temperature, or hardness will stress him out.

What NOT to Do (Common Mistakes)

Using carbon filters

Carbon removes medication from the water. This makes your treatment completely useless. If your filter has a carbon cartridge, remove it and just run the sponge or biomedia.

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Adding gravel or live plants

Most medications will kill plants anyway, and gravel makes water changes way harder. Plus, you need to be able to see everything happening in the tank—fish waste, medication residue, weird color changes.

Going too small

Those tiny betta cups at pet stores? Not hospital tanks. A floating bowl in the main tank? Also not ideal unless it’s an absolute emergency. Water quality crashes fast in tiny volumes, and sick fish can’t handle ammonia spikes.

Overdoing decorations

You need to monitor your fish, not play hide-and-seek every time you want to check on him. One or two simple hides are enough.

Using the wrong type of salt

There’s aquarium salt (for external infections and wounds) and Epsom salt (for internal issues like bloat and constipation). They’re NOT interchangeable, and you can’t use them together.

Figure out what you’re treating first, then use the right salt at the right dose. And heads up: Epsom salt and aquarium salt are NOT compatible—if you need to switch, do a 100% water change first and wait a couple days.

Skipping water changes

Most hospital tank treatments require daily or every-other-day water changes. Skipping them means medication buildup, ammonia spikes, and a sicker fish.

Yes, it’s annoying. No, you can’t skip it.

Dumping in random medications

Please don’t throw every medication in your cabinet at the problem. Using antibiotics at below-therapeutic doses breeds resistant bacteria, which is bad for your fish and bad for everyone else’s fish too.

Diagnose the problem first, then treat with the right medication at the right dose. When in doubt, consult a fish vet or experienced aquarist.

Maintaining Your Hospital Tank (Daily Routine)

Monitor temperature multiple times a day

Especially in the first few days. Heater malfunctions happen, and you need to catch them before they cook or chill your fish.

Check water parameters

In a small, uncycled hospital tank, ammonia and nitrite can spike fast. Test every 24 hours and do water changes if ammonia or nitrite goes above 0.25 ppm.

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Do water changes as directed by your treatment protocol

Most treatments require 25-50% water changes daily or every other day. When you change water, redose medication according to the new water volume.

For example, if you remove 2 gallons from a 5-gallon tank, you only need to add medication for 2 gallons, not the full 5.

Remove uneaten food and waste

Use a turkey baster or small siphon to spot-clean any poop or uneaten food. Sick bettas often don’t eat much, so don’t overfeed.

Observe your fish closely

Watch for changes in behavior, appetite, color, and activity level. Take notes or photos daily—sometimes improvements are subtle and you won’t notice unless you compare day-to-day.

How Long Does Your Betta Stay in the Hospital Tank?

This depends entirely on what you’re treating.

Most treatments run 7-14 days. Some conditions, like severe fin rot, might need longer. Others, like mild constipation treated with Epsom salt, might only need a few days.

Your betta can go back to the main tank when:

• Symptoms are completely gone
• He’s eating normally
• He’s swimming and behaving like his usual self
• You’ve completed the full course of treatment (don’t stop early even if he looks better)

After recovery, gradually reintroduce him to the main tank by floating him in a container to match temperatures, then slowly mixing small amounts of main tank water into his container over 30-60 minutes.

What to Do With the Hospital Tank After Treatment

Sterilize everything

Drain the tank, then use a 10% bleach solution to soak everything—the tank, decorations, heater (check if it’s safe to submerge), and any equipment. Let it soak for 10-15 minutes.

Rinse everything extremely thoroughly with hot water, then soak again in dechlorinated water with extra conditioner to neutralize any bleach residue. Let everything dry completely before storing.

Store it for next time

Keep your hospital tank gear together in one place so you’re ready when (not if) you need it again. It’s way less stressful setting up a hospital tank when you already have everything prepared.

Some folks keep a sponge filter running in their main tank’s filter compartment so they always have cycled media ready to go. Smart move.

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Final Thoughts

Setting up a hospital tank isn’t rocket science, but it does require some planning and attention to detail.

The key things: keep it simple, maintain stable water quality, match the temperature, and follow your treatment protocol religiously. Don’t overcomplicate it with fancy equipment or decorations.

Your sick betta just needs clean water, the right temperature, and the correct medication. Give him that, and you’re way ahead of most fish owners who panic and do nothing or throw random medications at the problem.

Think of it this way: a hospital tank is like health insurance for your fish. You hope you never need it, but when you do, you’ll be really glad it’s there.

Now go set yours up before you actually need it. Future-you will thank present-you when your betta inevitably does something dumb like biting his tail or decides that rock in the tank looks tasty and gets bloated.

You got this.