Do you need to do water changes?
It's a polarized world these days and water changes are no exception. There’s a lot of mixed feelings and opinionated people out there. Truthfully, there is no one answer for every aquarium out there. Every tank is different. Is it a large low tech aquarium that’s packed with live plants? Or are you creating a nano hi tech tank? Maybe you’re breeding fish that have super specific requirements…
6 Advantages of doing water changes
Most important thing is that it removes unwanted toxic chemicals such as nitrates and phosphates - though it’s not limited to this
Fish respond well to water changes - you can see that they get frisky and seem to enjoy the new water coming in, and also can trigger breeding - the ultimate sign of healthy fish
Algae responds poorly to water changes - there’s something about water changes that algae just hates
Gives us a chance to get into those spots that filters cant reach to remove organic waste - that’s nice way of saying fish shit
Opportunity to replenish minerals or reduce minerals that have built up
Kind of a hippie answer, but this is honestly how I feel but cleaning the tank is a time to get in touch with your tank, eye everything over. Check your fish out, see how your plants are growing… Be one with your aquarium
2 Disadvantages of doing water changes
Consumes water which is a valuable natural resource
Use it for your garden or on plants outside that aren’t your garden
Use it to flush your toilet
Pour it on a compost pile all year round
Takes time and energy - which is OK if your fish are healthy, but lame if they need changes
You can use a faucet adapter which makes water changes a breeze
So, what’s the answer?
If you want one single answer, that no one can argue with, though I’m sure people will …. It’s simply - What levels of chemicals are safe for your fish and will your tank exceed or deplete those if you leave it be?
You can pick an indicator chemical - for most people including myself that’s nitrates. Do some research on your livestock and see what’s safe for them.
The reality is, as someone who cleans tanks for a living is that most of the tanks I clean were setup by the owners not as ecosystem tanks but as budget friendly systems purchased through big box stores. The way that nitrates build up or get consumed before they can build up depends completely on how a tank is set up, how a tank is stocked, and how it is maintained.
What makes a low maintenance tank?
Often called an ecosystem tank, is a tank that doesn’t require water changes at all, or at least infrequently.
The idea is that decomposers and beneficial bacteria convert fish waste/ammonia to nitrates, a chemical that plants prefer to use as food or fertilizer. Once plants consume those nitrates and photosynthesize, they put oxygen into the water allowing fish to continue their healthy little lives with clean and oxygenated water.
Pretty cool when you think about it right… Like quite literally, fish turds get converted to plant material. Those green leaves you see, are recycling materials in your tank, converting little fishy turds to healthy vibrant plant growth. If you’ve ever seen or smelled a farmer spraying manure on their crops in the spring, it’s the same concept. Nothing new… People been taking advantage of the plant poop relationship as far back as history goes.
Catch is, you can’t go stocking your tank like crazy. This balance depends on waste not exceeding the plant nutrient uptake capacity. Often size is the biggest factor when it comes to how messy fish will be. For my little low maintenance tank, I have chili rasboras in here. It would be hard to pull this off with some large goldfish, cause they produce a lot of waste relative to their body size… Not to mention they also get large.
If this is for you, great. Enjoy a tank with some little fish poking around in the plants. Personally I love this look for a tank. It’s a little more natural looking and coming from someone who has multiple tank syndrome, I’m not complaining if some of them are low maintenance.
All that being said, it’s not possible for everyone to keep an ecosystem or low maintenance aquarium. What if you are one of those people?
Low maintenance tanks aren’t for everyone
Alright, so I just said it, low maintenance tanks are not for every fish, or every person. What are some cases where you absolutely need to be doing water changes?
Tanks with no live plants to consume fish waste. Sure - there are workarounds like denitrate and activated carbon but those need to be used in tandem with water changes.
Let’s look at some examples of tanks where you absolutely need to be doing water changes.
Tanks with large fish - even with live plants. South American cichlids and goldfish come to mind in particular. Then next level monster fish like Arowanas and such.
Aquariums that can’t have live plants because of herbivorous fish. Silver dollars and African cichlids.
Really sensitive fish like discus or elephant nose absolutely need water to be spot on. If not they are prone to getting sick and the solution for sick fish is usually extra water changes in tandem with meds on top of some more water changes. Mine as well stay on top of water quality to begin with and avoid those water changes.
Breeding tanks need to have clean water all the time, but a big water change with slightly lower water temperature can trigger fish breeding by simulating monsoonal rains.
Last but not least on my list, high tech planted tanks require water changes and excessive hands on maintenance for a few reasons. First of all, high fertilizing rates require that we remove those nutrients once a week and reset the tank’s water column. I’m not going to get into too much detail here, but if you’re interested you can check out some of my videos or articles that explore deep cleans for high tech planted tanks.
Other SITUATIONS
There are other situations where you could use chemicals, or do a water change instead. I always opt for a water change personally.
It’s also important to consider pH - if you live somewhere with low mineral content in your tap water, that can lead to wild pH swings. Learn more about ph, GH and KH. Even though it’s good to have an indicator chemical that you routinely check, it’s also good to check other parameters from time to time.
Or maybe your tank is stacked with limestone causing your mineral content and pH to skyrocket over time. A water change is a great way to keep those at a more consistent level. Ultimately it boils down to what fish you have and what they are capable of safely living in.
In both cases you could use pH up or down or another mixture of buffers and such but it seems easier and more reliable to me to just do a quick water change.
Another example would be brown water due to tannins. A lot of my clients worry about this when they just get set up with a new tank. It’s not a bad thing and the fish don’t mind… but one option is to find some matrix to absorb the tannins, or… you guessed it. Do a water change.
The Table
OK, let's go over this little table that I put together showing what levels are acceptable for fish. Keep in mind, I looked up these values from a number of different sources so there might be a little wiggle room… But when in doubt, play it safe. Why make your fish live in poop water if they don’t have to… Let’s put it this way, if you flush your toilet after dropping a deuce, why not pass that same courtesy on to your fish?
How much water to change?
I generally do 50% water changes. It’s just the frequency that changes. For sensitive fish, it makes sense to do more frequent but smaller water changes. Ultimately you’ll have to monitor your water quality to determine how often you need to be doing water changes. A quick note though on nitrates math. Nitrates are not logarithmic like pH. If you have 40 PPM nitrates and do a 50% water change, you should have 20 PPM afterwards.
Finishing notes
So do you need to do water changes? Hopefully this was helpful in explaining if and when you need to do water changes!
Let me know what your water change habits are or if you have any questions~ 💬
