When I first started out writing about goldfish bowls, my goal was to discourage people from using them at all costs.
But you know what?
The deeper I researched, I started finding more and more information that made me question my position…
WAS it really impossible like so many said?
People making headlines with fish in bowls that had lived multiple decades. Historical evidence showing successful keeping of goldfish in bowls for centuries gone by. Arguments against it that didn’t hold up to the scientific evidence.
So I set out on a mission to learn the truth for myself.
I was NOT going to recommend something to people unless I could do it myself – successfully.
It’s no joke:
Many people struggle with keeping their fish alive in bowls.
But I had a theory – a theory with workarounds to overcome the common problems that lead to failure…
(Yes, I’m a bit of goldfish geek.)
I bought all of the supplies discussed in this article (that I didn’t have already).
And finally, I set off to Walmart and bought myself a $4.68 orange Ranchu.
During this process, some of my theories shifted as I learned through real-life experience what works and what doesn’t.
That fish – “Wally” – is still thriving in a stable, fully cycled goldfish bowl that never once saw an ammonia spike (photo above).
Everything in this article comes from what I’ve learned through this process and hours of research.
I hope it helps you!
How to Set up a Goldfish Bowl
Want to learn how to set up your goldfish bowl the RIGHT way, so your fish can live a happy, long life?
You will need the following supplies:
- Goldfish bowl (2 gallons minimum, 3 gallons is better)
- Bowl filter (with carbon cartridge) or canister filter
- Air pump and Airline tubing
- High quality replacement carbon media
- Bowl Heater (if keeping fancy goldfish like Fantails)
- Seachem Matrix – Porous filter media/substrate
- Prime (dechlorinator/ammonia and nitrite binder)
- ATM Colony or Quickstart (bacteria culture startup)
- Plants – Pothos, Anubias, Hornwort or Lucky Bamboo are some good ones
- Siphon (for partial water changes)
1. Picking out the Fish Bowl
The biggest limiting factor with bowls is the fact that they are so small.
When choosing a goldfish bowl, get the biggest one you can find. The bigger the better because it will help to keep the water parameters more stable.
I can’t emphasize this enough.
The typical little 1/2 or 1.5 gallon ones from the pet store are sold for betta fish – NOT goldfish – and can be really hard to keep clean.
Which is why I recommend using a bowl that is at least 2 gallons for one fish.
It will mean less work for you and more stability for your fish.
A large plastic goldfish bowl – or acrylic or glass – works great.
This plastic one is 3 gallons – the biggest I could find – and is super durable (and cheap).
Here are my observations on plastic fish bowls:
- The opening is a bit small though for my preference, and though the filter does fit in it with a bit of squeezing it doesn’t have as much room to move around in – but this really isn’t a big deal if you leave the filter in during cleanings. It think keeping it in during cleanings is unavoidable as you risk breaking the filter each time you squeeze it.
- The smaller opening means less surface area. While less surface area means less room for oxygen exchange, oxygen exchange is not completely dependent on surface area. It happens when you filter or change the water as well.
- One thing that might bug some people is that plastic scratches more easily than glass, especially if you are trying to clean the bottom by swirling the substrate around. I’ve found you can mitigate this a bit by emptying the water and substrate into a 5 gallon bucket and doing the swirling action in there instead, but some scratching is going to be inevitable unless you use a sand bottom.
- You don’t really now how good of quality the plastic is or if it leaches any chemicals into the water.
So I personally really like this glass one that’s nearly 4 gallons.
The opening is much more comfortable to work in, offers better oxygen exchange and it has a bigger volume overall.
With good water quality, you could probably keep 2 goldfish in it.
For what it’s worth, many goldfish bowls in ancient times were much larger than what we commonly see at pet stores. Some were more like big clay pots (kinda like this) and the fish were only viewed from above. Sometimes ancient Japanese goldfish owners carried their bowls around as a fashion statement!
Which brings me to my next point:
2. Filtration Equipment
You don’t absolutely have to use a filter if you change the water on a daily or twice daily basis…
But most of us probably don’t want to do that.
A filter reduces the maintenance needed for your bowl so you can go for longer in between cleanings. It also allows you to add charcoal which can help with removing growth hormones from the water.
Installing a goldfish bowl filter is the next step.
An undergravel bowl filter (I really like this one) is what will keep water moving through the substrate and allow better growth of your good bacteria colony.
The right kind will do something else very important…
… Oxygenate the water.
Personally I wouldn’t use any other internal filter on a goldfish bowl because it takes up too much room – or if it doesn’t, there isn’t enough room for the biological media.
Keep in mind that this substrate will still need to be regularly cleaned to remove the debris.
You will want to keep the carbon going for the first 6-8 weeks that the bowl is set up.
This will help protect the fish from high ammonia levels until the bacteria colony gets fully established.
After that, you could remove it if you want to keep your fish small (carbon absorbs growth inhibiting hormones) – but you’ll want to keep the cartridge as I’ve found it really helps diffuse the current.
Be sure the water level never goes below the top of the filter or it won’t work!
For the ULTIMATE bowl filter setup…
… A small canister filter in addition the undergravel filter would be even better at processing all that ammonia.
That means you could even get away with keeping 2 fish instead of 1.
This would help to reduce maintenance even more. It would also add a bit to the total water volume.
One thing about canisters is you don’t want too much flow or you’ll stress your fish.
Higher water turnover = more current.
(Goldfish like slow-moving water.)
This one turns over a low number of gallons per hour (79), but if you want to set your filter on the floor instead of by the bowl, the mini SunSun canister would work better (100 GPH). Just be sure to use a spray bar to help prevent the stress of current.
The best media to use in your canister is, in my opinion, large ceramic porous media.
It doesn’t trap debris, requiring less cleaning.
Just be sure to put a sponge over the intake to prevent debris getting sucked up.
If you decide to only run a canister filter without an undergravel filter, you’ll just want to make sure you add an air stone so your fish get enough oxygen (be sure to use a very small pump to avoid excess current).
Maybe you could put some sand on the bottom instead (goldfish love sand).
It’s your bowl, your rules.
You can also build your own filter as shown below to put a plant in the top (though this particular design does not take advantage of the surface area in the substrate and is better for low-waste producing fish like bettas).
But if you can figure out a way to rig some kind of DIY external filter for your bowl, more power to you (beware of too much current though).
How about that charcoal (aka carbon)?
The carbon will help keep the dissolved organics low and can help reduce growth hormones in the water.
The stuff that comes with the filter is probably going to be low-quality. Low-quality charcoal has been linked to issues like hole-in-the-head, so I recommend throwing it out and replacing it with good carbon like Matrix Carbon.
Good, high-performance carbon will also help keep the toxic ammonia levels down.
You will want to replace it weekly or every other week if your colony is not established (indicated by your water test results). Eventually, you can stop using it – but it could take longer than normal if you don’t cycle your bowl first.
You should know this:
Carbon. Is. Messy.
No matter the brand, no matter how much you rinse it…
The stuff will get all over everything in your bowl UNLESS you put a little bit of batting or polyfilter pad cut in a circle (what I did) at both ends of the cartridge and “sandwich” the carbon in between.
3. Adding Substrate
When it comes to stable water conditions, bowls are at a big disadvantage to tanks.
Because bowls don’t have much room to put anything in them (and any kind of internal filter such as a sponge filter takes away from valuable water capacity), this leaves minimal room for a place for beneficial bacteria to grow.
(Aka limited surface area.)
So we need to maximize whatever space we can to grow our “good bugs.”
So we need to rely on the substrate itself to house our bacteria. That’s where the most room is to grow our colony.
Basically we’re going to use the stuff at the bottom of the bowl for our filtration.
Now… what stuff is that?
I don’t recommend gravel because it is a choking hazard and it really traps the debris a lot. Not to mention the core is solid, so there isn’t very much room for bacteria to grow on it (more on that in a minute).
Marbles are a popular option, but their surface is so slippery and smooth and the inside is solid that it doesn’t provide optimal colonization areas for beneficial bacteria either.
Porous media like this kind is affordable and offers tons of surface area for the bacteria to grow on due to all the little pores each piece has. It also supports the special kind of bacteria that remove nitrate.
The surface area of the stones in this bottle has enough room to grow a bacteria colony large enough to filter a heavily stocked aquarium over 10 times the size of your 3 gallon goldfish bowl.
It’s size also makes it impossible for goldfish to get stuck in their mouths – and it’s far easier to clean.
(Much better than gravel.)
There are two ways to configure your substrate.
1. Porous media ABOVE the UG filter [Traditional Setup]
You will want to be sure to remove any pieces that could fit in the fish’s mouth and potentially get stuck.
Here’s a tip:
This media is pretty light-weight, meaning it can be difficult to keep the filter weighted down. But the secret is to add a handful of 1-2″ (washed) river rocks in with the porous media. No more floaty filter 🙂
Any poop (and sinking food) goes down between the rocks.
If you keep fancy goldfish (which are sensitive to waste buildup), this can necessitate a mid-week cleaning.
When you try to do a 50% water change with a siphon, the rocks get moved around and the filter can get exposed or even start floating.
Not a huge problem, but an annoyance to me.
It can also be difficult to find good-quality floating foods – which can be a big issue when fancy goldfish have more specialized diet requirements.
This setup works pretty good. But I feel this method is best for slim-bodied fish who aren’t so sensitive to higher dissolved organics, and for owners who don’t mind using floating pellets or flakes.
2. Porous media BELOW and around the UG filter [Advanced]
Let me explain what I mean by this:
Using the smallest size of the Seachem Matrix pebbles, you line the bottom of the bowl about 1/2″ deep.
Over that goes the UG filter plate.
On top of the filter plate you put a layer of polyfiber media cut into a circle, with a couple of holes for the tube connections on the plate to poke through.
Finally, a 1″ layer of CaribSea Crystal River aquarium sand (which has a coarse grain) goes on top.
The large grain size allows the water to flow through it easier.
The best part?
It is INCREDIBLY easy to vacuum. The larger sand grains fall to the bottom during vacuuming while the debris is sucked up.
The circle of polyfiber should be big enough that no sand can get down between the edges, but not too large that it buckles and causes gaps.
This fiber can be replaced once every year or so.
4. Decorations & Plants
While sunken ships, castles, fake plants and other decorations might look cute in your bowl…
Please don’t put anything frivolous in it.
Everything additional you put in there takes away from the all-too-precious water volume your goldfish bowl can hold. If it’s going to be in there, it needs to have an important purpose.
You can – and should – add live plants.
Live plants will help to take up nutrients from the water column and keep the nitrate levels lower. They also provide hiding spots for the goldfish.
I like growing plants partially submersed as well as fully submersed.
The fully submersed ones help to hide the roots of the ones growing in the top, as well as provide fun hiding places for the fish.
- You can add Pothos to the top of the bowl which trails over the sides. Pothos is a nutrient-hungry plant that grows roots in water and sucks out nitrates and contaminants from the water, helping to keep the tank cleaner.
- Lucky bamboo is another excellent option. Its leaves should not be submerged, but the roots can be left in the water and will pull nutrients – especially nitrates – out of the water.
- Anubias are a great choice for goldfish if you want a submersible plant that won’t get munched.
- Hornwort is fast-growing, eats up nutrients quickly and can grow floating or rooted – though it can shed unsightly needles.
- Bacopa (Moneywort) is a pretty little plant.
To hold it in place, you can wrap a thick little wire (I use the plastic coated kind used for hanging picture frames) around one of the stems and loop it over the edge of the bowl (if your bowl has a rim).
The more plants you have the better – they really can help with water quality.
It also looks fantastic 😉
(Remember – any new plants should be quarantined!)
The nice thing about fish bowls is you have more options with the plants inside because the goldfish don’t get to be monsters that mow everything down.
5. Adding New Fish
Each fish you add increases the wasteload and increases the chances something will go wrong FAST with your water chemistry.
At the same time, most goldfish like companionship.
When you are first starting out, only one fish might be a good idea so you can get a beat on your water quality.
If you don’t want your new goldfish to die shortly after the first week or two that you get them (a common problem with bowls) it’s really important to cycle the bowl first before adding fish using liquid ammonia (yes, you CAN cycle a bowl, and the better substrate you use the more powerful your colony will be).
That’s because the ammonia levels skyrocket once you add fish to a brand new setup with no good bacteria.
Or if you DO add fish without cycling, do lots of water changes (if you have a carbon filter, 50% daily or every other day) initially and feed super sparingly for a few weeks.
Adding beneficial bacteria filter supplement to get your culture going is also highly recommended.
If at any time you notice your fish is not as active – or seems hyperactive – do an immediate 50% water change.
Caring for your Goldfish Bowl Regularly
Here’s how to clean a goldfish bowl:
- Without a filter, twice daily 50-100% water changes are recommended. This is because, according to my tests, the ammonia the fish produces builds up so quickly that even 100% every 24 hours is insufficient to keep it in check.
With a filter, once a week 100% water changes is recommended (one partial water change mid-week is a good idea as well using a turkey baster or small siphon to remove debris from the bottom). You might be able to get away with going longer if you use a bigger bowl, depending on your water test results (ammonia always 0, nitrates should never go above 30ppm), however the carbon should still be replaced weekly.
- It’s a really good idea to age the new water overnight first with an airstone before you do your water change. This simple step will help gas off bad stuff from the water source. Don’t forget to use a dechlorinator first before aging.
- The fish and any plants should be transferred into a separate container from their bowl water using your clean (residue-free), gentle hands. Remove the filter apparatus (if desired).
- Use your hands to agitate the substrate around in the bowl, swishing it around well before transferring it to a bowl of fish water. Rinsing it with hot tap water can harm your beneficial bacteria colony you need on your substrate. If you feel like it is not clean enough, more water may be required. Any extra water you clean it in should be dechlorinated and aged overnight (such as in a bucket).
- Dump the old dirty water on a plant or down the sink. Use a soft cloth (no soap) to wipe down the residue on the inside of the bowl.
- Change the charcoal in the filter for fresh (it doesn’t usually last more than a week or so).
- Replace the equipment and refill the bowl with aged, aerated water that has been previously dechlorinated. The fish can now be transferred back in by hand (the old water they were in should be discarded as well).
It’s important to test your water with a test kit before you do a water change every week so you know if your water is staying safe for your fish.
I would highly recommend keeping an alert pack in your bowl too to monitor the pH and ammonia 24/7.
If your pH is low (you don’t want it to be below 7), up your water changes and make sure your water source doesn’t have a low pH.
Remember to keep the bowl out of the sunlight, or it can rapidly overheat and hurt the fish.
Worse yet – direct sunlight can actually cause a glass bowl to light something on fire due to its “magnifying glass” effect!
You can put a screen or shade around the bowl if it’s located in an area that gets direct sunlight during part of the day.
Feeding Your Bowl Fish
Overfeeding is a BIG problem – many times deadly – when a fish is living in a little space.
A goldfish bowl, even one with a colony of good bacteria, is still a delicate ecosystem.
Only feed the fish it’s staple diet food once every day or every other day, just a tiny amount.
Less food = less waste, and less waste = less toxins in the water.
If you use a substrate other than sand or bare-bottom, I really recommend using floating foods only.
This is because sinking foods will fall down between the rocks where the fish can’t get to them and pollute the water.
So floating pellets or flakes are best.
Be sure to provide access to leafy veggies daily though to let your fish satisfy its foraging behavior.
Finally, if you get your fish from a pet shop or Walmart or a fair…
Don’t forget to quarantine.
Quarantine is more than isolation, it requires using treatments to rid the fish of internal and external parasites (most are invisible to the naked eye).
Unless you do this CRITICAL step…
Your goldfish could end up dying in the next few months, no matter if you do everything else right.
Most new goldfish come with a hidden secret… a load of parasites.
At first, they might not have many, and could seem normal to all appearances.
The fish can live with them for a while, but eventually they may end up multiplying to out of control numbers and cause the fish to get weaker and weaker… until it can’t take it anymore.
Now it’s Your Turn
What you do with this information is up to you, and I hope it helps save someone’s pet.
Are you realizing you need to make some changes to your bowl?
If it makes you feel better… yes, I admit it:
I even used to have goldfish that lived in a bowl like most people have (my fish didn’t last long!).
So pet ownership is a learning process for all of us. We make mistakes. We learn new things along the way.
Ultimately, we all want the best for our fish.
Did you learn something new?
Share your thoughts in the comments below!