Zero-Waste Pet Care Guides

The Eco-Friendly Fish Tank Guide

Can you keep pet fish and not have a major impact on the environment? Whether it’s the goldfish you win at the school fair or a tank purchased and set up from an aquarium store–or something in between–there are a few considerations to making your tank as environmentally friendly as possible. These tips will not only help lessen your tank’s impact on the planet but will save you a little money, too.

The topic can be broken into a few main points: the fish, the tank, and the maintenance. Let’s wade in (I couldn’t help myself), shall we?

Can keeping pet fish be eco-friendly? Find out everything you need to know to operate an eco-friendly fish tank in your home! is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to As an Amazon Associate I earn from qualifying purchases. 

Can pet fish be eco-friendly?

Walk into any pet store and you’ll be met with a wall of tanks filled with all sorts of fish. From fish genetically modified to glow to the schools of tiny community fish, you can find it all at a pet shop. So, how do you know which fish to get if you’re looking to create an eco-friendly fish tank?

First, it’s important to understand where your fish come from:

Aquarium keeping can also have hidden environmental costs upstream. In some parts of Southeast Asia, where the vast majority of the world’s saltwater “ornamental” organisms come from, fish are caught using squirt bottles filled with cyanide, which stuns the animals and makes them easier to extract from coral reefs. But the chemical can also damage the corals, as well as other organisms living in the reefs—not to mention weakening the fish so that fewer of them survive transport. (Keeping fish healthy isn’t just an animal-rights issue, after all, it’s also an ecological concern. The fewer animals that survive the process, the more intensive the harvesting has to be.) When buying wild-caught fish, look for those that have been captured with hand nets rather than chemicals.


Sustainable collection is less of an issue with freshwater aquarium species, since 90 percent of them are farm-raised. 



OK, so we just drew the first line in the sand, so to speak. Err on the side of freshwater aquarium species, not saltwater. (There’s another good reason for this distinction, too, when it comes to the tank, but more on that in a minute.)

When we decided to add a fish to our family, it was because of the specific tank, which I’ll get into in a minute, and the purchase came with a coupon for a free Betta from Petco. So, that’s what I got. In the wild, bettas live in shallow rice paddies in Thailand, Vietnam, Cambodia, and Laos. They’re not the colorful fish you see in plastic tubs in pet stores. Those have been bred to look that way.

A quick aside about bettas: They shouldn’t live in a vase or a cup or a beer stein on your kitchen counter. They need more space than that, and they deserve oxygenated water. Even though they’re often sold like that, don’t do it. Read more about betta care.

So, you’ve picked out your farmed freshwater fish. Now what? Well, he or she needs a tank! Let’s look next at how to minimize the impact of your fish tank.

Can fish tanks be sustainable?

I remember as a teen babysitting for this family that had a built-in aquarium along one entire wall of their living room. To access the filters, pumps, equipment, and so on, you had to enter a doorway from their laundry room. The thing mesmerized me, but in hindsight… wow. That thing probably consumed an enormous amount of energy!

Plus, it was a saltwater tank, and saltwater tanks just use more energy than freshwater tanks in general because it requires more effort to keep it working properly.

This is also a case where smaller is much, much better. The bigger the tank, the more water, the more energy, the more stuff required to maintain it!

The fish tank we purchased is a hydroponic system that does more than keep our betta alive.

BTW, I failed to mention: I allowed my two-year-old daughter to name our fish. She named him Tacofish. Shrug emoji. I posted a pic of him on Instagram when he came home, so meet Tacofish! 🙂

So, this is the tank we bought. While I absolutely love it, it’s definitely NOT self cleaning like it claims. However, we’ve had so much luck growing batches of microgreens on the top, and Tacofish is super happy in the tank, that the weekly clean is no big deal.

The tank came with gravel for the bottom, but if I were to do it again or advising someone else on setting up a new tank, I’d strongly recommend glass marbles like these or stones like these because they’re easier to clean and #noplastic.

Here’s where I erred: Knowing bettas need places to hide to be happy, I picked up a cheap decorative object to go in the tank when we were cashing in our betta coupon. It’s plastic. I wasn’t thinking.

But, whatever fish you get will need places to swim and hide. If you choose to go with live plants, you’ll avoid the plastic trap BUT you’ll likely need additional lighting controls, which will add to your energy consumption. If you go the live route, aim for LED lights to help offset that.

OK, so you have your farmed freshwater fish living in a small tank! Now, how do you keep it fresh, clean, healthy, and environmentally responsible? Let’s dig into a few maintenance points.

Maintaining an Eco-Friendly Fish Tank

Here’s an awesome way to use your tank to help the earth: Water your plants with the dirty water when you do a change!

Can you irrigate plants with aquarium water? You certainly can. In fact, all of that fish poop and those uneaten food particles can do your plants a world of good. In short, using aquarium water to irrigate plants is a very good idea, with one major caveat. The major exception is water from a saltwater tank, which shouldn’t be used to water plants; using salty water can do serious damage to your plants – especially potted indoor plants.


Yet another reason to skip the saltwater tank!

You can also water your houseplants with the discard water if outdoor gardening isn’t your thing or it’s not growing season.

Schedule regular cleans and don’t skip ’em. It’s good for the fish, of course, but a clean filter runs more efficiently, too.

Once your dear fish passes on, don’t flush him. Instead, bury him in your garden so decomp can help your plants.

Finally, if for some reason you can no longer care for your fish, do not flush them! First of all, that’s super inhumane, but it’s also a terrible idea to introduce a non-endemic species. Instead, re-home your fish by listing the full tank, all the supplies, and the little guys and gals on a site like Nextdoor.

There you have it: Everything you’ve ever wanted to know about keeping an eco-friendly fish tank!

Now it’s your turn: What questions do you have? I’m here to help! Leave them in the comments below!

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  • Kerry

    I realize this article is a year old, but I had to comment. A betta is an intelligent fish and needs a complex environment to explore. It also requires a 5 gallon or larger aquarium with a heater (78-80 degrees). This tank is a cruel option if you ask me. A more eco-friendly option would be a gently used second hand 5-10 gallon tank from Craigslist or Nextdoor – let’s just say there are MUCH better options than this betta death trap. (No mention of the nitrogen cycle, beneficial bacteria keeping the tank in balance, etc. It’s like this is just an ad and no research was done.)

    • maggieZWP

      Hi, Kerry! Thanks for your comment. I had to sit on it for a couple days, which I’ll talk about in just a sec, but I wanted to first say that your passion for bettas is wonderful. I’ve worked in the pet industry for a very long time, and it always touches my heart when someone has so much love for animals that are often overlooked. I’m also thinking of our rat friends, snakes, and so on. Thanks for caring so much about bettas!

      It took me a couple days to get back to you because I wasn’t entirely sure the purpose of your comment. In this space and at my other pet site, I strive to embody the principle that we are all doing are very best AND that we could all do a bit better. Being kind, compassionate, and understanding goes a long way for me in achieving those aims. I never want to come across as angry or judgmental because–and here’s why this took me a couple days–it shuts people down. I assume you left this comment because of your passion for bettas, so in my experience, the animals would be so well served with the same information delivered in a more compassionate manner. I can tell you’re angry, though, and I wanted to address your points thoroughly.

      I’m not a ichthyologist. Hopefully nothing led you to believe that. What I wanted to do here was NOT to provide a fish care guide. I’m not the person to do that, and I’ve been on the lookout for an expert who could do so. Is that your field? It would be great to get more details about your background in case there’s a fun fit! Someone to address the water balance and so on would be great. This post wasn’t meant to be that by ANY stretch. Fish tanks, not fish.

      And while I agree with you that second-hand is the best way to go whenever possible, I’ve yet to find a hydroponic system that was a complete cycle to grow food all year long. Buying new was the only option after a year+ of looking. I get your dig that this reads like an ad because it’s the only brand I mentioned, but I assure you there’s no paid partnership and I referenced it–along with several criticisms–because it’s what I have first-hand experience with. I’ll never talk about something I haven’t touched or used. And not to quibble, but there actually is a heater.

      As for the fish size, well, I’m at a loss. I spoke in depth to the person in the fish department about the tank, and he said the standard is one inch of fish per gallon of tank, so a 2-inch fish in a 3 gallon tank was fine. Honestly? I trusted that guy because he worked in a fish store. Again, if you’re an expert, I invite you to consider a guest post or an interview to shed light on the topic.

      Finally, I’m hoping you intended your comment to be a discussion, but my suggestion if you’re open to it is to take your expertise and your passion to the manufacturer of this, as you called it “betta death trap” and strive to use your strong voice to effect real change! That’s what we’re all on this earth to do, to help however we can, and it sounds like your passion for bettas might be just what they need to hear!

      • May

        It’s not necessary for a person to be an ichthyologist to do a bit of research on a living animals needs before purchasing one. When you say that, it comes across as being defensive about your lack of research.

        You’re right that marketing does have a major impact. Ie why can’t I put my Betta in this tank if the packaging shows a Betta in the tank? It’s problematic, but maybe you can also voice your newly learned knowledge to these companies and have a positive impact there!

  • Charlotte

    Hi, I quite liked your article there’s just a few things I feel aren’t fully considered and maybe misleading. Firstly the recommendation that smaller tanks are better ecologically may be true, but there are 2 serious negatives that you didn’t mention; tank mates and stability.
    Aside from male bettas, most small fish are social and need to be kept as a group. 4 is the bare minimum but more than 7 is preferable, this means small tanks under 10gallons aren’t actually suitable for fish.
    The other issue is stability, even with a heater and frequent water changes it’s really hard to keep stable water. The nitrates build up very quickly then suddenly reduce due to mainence, room temperature fluctuates with heaters or air conditioning which makes the temperature unstable, this causes stress and disease in fish and algae or bacterial blooms for the tank. and any additives like ferts, declorinators and medication are a lot harder to dose accurately without special pipets.
    When it comes to fish welfare bigger is always better, but like your article says the footprint on environment also increases.
    I’d make a few suggestions to be more eco-friendly fishies that doesn’t compromise their health:
    Set up a walstad tank, it’s a mini bioactive ecosystem that doesn’t use a filter
    Use rain water for water changes, this way you don’t need to add chemicals and saves drinking water.
    Place tank near a window for natural light (ensure you have an option to block the sunlight to prevent excessive algae growth)
    And if you don’t want a heater choose fish native to your area that prefer your natural temperatures, wild form fish can usually handle temp changes better than those breed for beauty. (Personally I think their natural beauty looks better too) of course make sure they are captive bred not to harm populations in the rivers and streams.

    This is just to add to the many good points you had, hydroponics is a great idea and like you said tank water is a wonderful fertiliser for all plants. I especially appreciate you reminding everyone they can rehome their fish, they are probably the most neglected and abandoned pets and it’s as easy as posting an ad online to find a new loving home.

    I don’t know much about bettas so can’t offer any insight on their needs, but people in pet shops are there to sell you things. Their advice is unreliable at best, no matter how nice of a person they seem. The inch to gallon ratio is outdated due to not taking species requirements into consideration. Fish like goldfish and oscars produce heaps of waste compared to something like angelfish and ghost knives of the same length. Some fish also need more room to swim, not having enough causes aggression issues in many schooling species or skittish fish to hit the sides. Always do lots of research beforehand and if the shop assistant gives advice just double check or have a think about it, they prey upon newbies to make a quick buck, everyone’s been fooled at least once. (I was sold 2 oscars and a blood parrot for my first fish tank, not compatible species and require a massive tank. Also not fish for beginners.)

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