Arguably no topic causes more debate and argument amongst aquarists than water changes in planted aquariums. One website will tell you to change 50% every week, another that you never need to change any at all and another somewhere in between who’s advice changes daily depending on who you’ve spoken to that day.
The reality is that different tanks need different water change schedules depending on the goal you have for your aquarium and how it is actually running. You freshwater stemweed paradise will require entirely different maintenance to a low-tech planted tank filled with slow growing anubias and java fern. The problem is nobody really differentiates planted tanks into these categories.
Instead of blindly following someone else’s schedule let’s take a look at exactly how water changes benefit your aquarium and how to properly tailor your water change schedule to YOUR aquarium and how it is running.
The Importance of Water Changes in Planted Aquariums
There are several reasons we perform water changes in planted tanks. The main 3 factors are nutrient dilution/reset, pH buffer replenishment and waste removal.
While fish tanks need water changes to combat rising toxic nitrogen levels from fish waste, planted aquariums benefit water changes in multiple other ways because plants (and bacteria) add additional factors into the water column.
Nutrient Dilution / Reset
Aquatic plants absorb available Nitrogen (Nitrate & Ammonia), Phosphorus and Potassium from the water column at different rates dependent on the species of plant, intensity of lighting, availability of CO2 and how fast the plants are growing.
Fast growing stem plants may easily uptake 90% or more of available nitrates from the water column every few days while slower growing plants such as cryptocorynes barely seem to register a decrease in available nutrients (Read more…).
With every water change we dilute these nutrients down to manageable levels. Without regular dilution high nutrient levels will eventually lead to algae problems or begin to limit the growth of your plants.
pH Buffers
Aquatic plants consume CO2 during the day which affects KH (carbonate hardness) and thus your tanks pH stability. Buffer capacity will slowly be used up over time as well and regular water changes help to top up this buffer capacity.
A lack of buffering capacity in your aquarium will cause wild pH swings and stress your fish as well as destabilise your biological filter.
Waste Removal
Even the cleanest aquariums produce waste. Fish produce ammonia during normal metabolism and feedings. Plants will slowly die off and decompose adding to this waste load. Beneficial bacteria use up trace amounts of many nutrients and also add to the total waste produced in your aquarium.
Water changes help to physically remove these dissolved organic compounds from your aquarium.
Plant Allelochemical Dilution
Plants produce many different types of chemicals that are released into the water column. Some of these chemicals are used to inhibit the growth of algae and even other plants. While this is generally a good thing an excess build-up of these chemicals can actually begin to harm your plants.
Regular water changes help prevent this toxic build-up from occurring.
So how often should YOU change water in your planted aquarium?
Recent studies have shown that its not how big your tank is or how many fish you have that matters but rather how heavily planted your aquarium is AND how fast those plants are growing that determines how quickly these various processes happen.
Lets take a look at each individually.
High Maintenance Planted Tanks
A planted tank would fall under this category if it has the following:
- High plant density
- Fast growing plants
- CO2 injection
- Very bright lighting
This style of planted tank would include most freshwater stemweed tanks. Typically these aquaria will consume nutrients very quickly and will benefit from regular water changes in addition to fertilization.
Weekly Water Changes
An EI fertilization regime explicitly calls for large water changes every week (link). This is because every water change you perform effectively resets the nutrient levels in your aquarium back to a known starting point preventing any one nutrient from becoming limiting or building up to excessive levels.
Larger Changes = Better
Larger weekly water changes work well in these systems because your plants are capable of consuming very large amounts of nutrients if all other elements are present in sufficient quantity. A 50% water change removes around half of all excess nutrients while replenishing your aquarium with fresh minerals found in tap water.
How to implement
Pick a day of the week and perform water changes on that same day every week. I personally change my water the day after my biggest fertilization day to help push my nutrient levels back down.
Use a gravel vacuum and suck up any detritus that has collected on top of your substrate but try not to disrupt any established plant roots.
For a 200 litre tank this would equal 100 litres of water which would take approximately 45 minutes to remove and replace including time to refill your aquarium and match temperatures.
Budget
Larger weekly water changes will increase the amount of dechlorinator you use significantly. A 200 litre tank with 100 litres of new water being added each week would use around £15-20 worth of dechlorinator per month not including the additional heating costs.
You will want to factor this into the monthly running cost of a high maintenance planted tank.
UK Seasons
If you live in the UK you will notice the temperature of your tap water changes drastically between summer and winter. In January your newly added water may be up to 8°C colder than the water already in your aquarium. During summer you won’t have this problem but may experience the opposite problem with chloramines being more prevalent during summer months leading to a need for stronger dechlorination.
Moderate Maintenance Planted Tanks
This is where most planted tanks will fall. Moderate plant density, using standard flourescent or LED lighting with no or minimal CO2 injection. Growth rates in these tanks will be slower and nutrients will not be used up as quickly.
Bi-Weekly Water Changes
Aquariums that fall into the 20-50 gallon range with moderate plant density do well with 20-25% water changes every two weeks (link). This spreads out your nutrient dilution enough that it falls in line with how fast these moderately lit systems consume available nutrients.
Extended Intervals on Heavily Planted Systems
A mature tank planted very densely but run under moderate lighting conditions may be able to get away with pushing water changes out to once every 2-4 weeks (link). The only stipulation here is that your tanks planted volume must be large enough to process all of the waste generated and consume the nutrients produced in between water changes.
Bioload is More Important
Fish biomass has a much greater impact on how often you need to change water in moderate systems than it does heavy planted tanks. A 75 gallon tank stocked full of 10 adult angels will need more water changes than the same tank setup with 6 cardinal tetras. Determine your fish bioload based on how big your fish will eventually get, not how big they are now.
Planted Substrates
If you are using a planted substrate such as aquasoil you should expect nutrient releases to occur as well. Aquatic soils release nutrients into the water column very slowly over the course of many months, even years.
During the first 6-8 weeks after setting up your aquarium you may need to change water more frequently to account for the nutrient releases from your substrate. Thereafter you can probably slow your water changes way down as your plants become established and begin to utilise the nutrients being released.
Test Your Water Parameters
Heavy maintenace tanks can pretty much get away with never testing their water again after establishing their initial water change schedule. Moderate systems benefit from occasional water tests. Cheque your nitrates once a month and if they get consistently higher than 20ppm or lower than 5ppm you can adjust your water change frequency upward or downward accordingly.
You should never …
Mistake #1: Follow recommended schedules without taking tank maturity into consideration.
New aquariums go through what is commonly referred to as a stabilisation period. During this time algae such as diatoms are very common, appearing in most tanks within 1-3 weeks. Diatoms and similar algae will usually disappear on their own within 2-6 weeks once the tank has balanced out (link).
Increasing water change frequency during this period will usually stress the natural stabilisation process rather than helping it.
Mistake #2: Ignore how much you feed your fish.
Overfeeding is just as much responsible for nutrient bulding and algae blooms in planted tanks as too few water changes. Instead of attempting to change more water to compensate for overfeeding problems (hint: you can’t), cut back on the feeding first and stick to your regularly scheduled water changes.
Mistake #3: Change too much water in a low-bioload system.
Yes it is possible to over-change your aquarium. Heavily planted tanks with very few fish have been known to benefit from less frequent water changes. A small 150 litre tank planted with slow growing anubias and java fern and only stocked with 6 small community fish might only require 15% water changes once a month.
Mistake #4: Temperature shock your fish with large water changes.
If you live in the UK you will notice the temperature of your tap water fluctuates wildly between summer and winter. Adding 50 litres of water to a 100 litre aquarium in January can reduce the overall temperature by 3-4°C instantly which will not only stress your fish but can also crash your beneficial bacteria colonies.
Mistake #5: Treat water changes like magic algae fixes.
Increasing water change frequency is rarely the solution to persistent algae problems. Before pulling out your water hose try and figure out what the underlying cause of the algae problem is. Is it too much light? Fluctuating CO2 levels? A nutrient deficiency? Addressing the true cause is always a better solution than blindly changing more water.
Mistake #6: Assume every planted tank is the same.
A 30 litre nano planted tank will require completely different maintenance than a 200 litre low-tech community aquarium. Tank volume, planted volume, lighting levels and fish bioload all play a role in determining how often you should change water.
Source Research
Research has shown aquarium water change frequencies should line up roughly with the rate at which nutrients are consumed and wasted produced in planted aquariums (source). This is exactly why EI methods advocate for large weekly water changes. By restoring nutrients back to a known starting point every week you prevent any one element from becoming limiting or building up to excessive levels.
Additional research has shown new aquariums go through a predictable set of algae cycles (source). Diatoms are the single most common algae to appear in new tanks and should show up within 1-3 weeks of starting your aquarium. Once established they will usually die off within 2-6 weeks on their own.
Another study detailing nutrient cycling in planted aquariums verified that planted density and plant growth rate are the biggest factors affecting nutrient consumption rates. Tank size and fish load were less important than overall planted volume.
Breaking it down by tank type
- Nano tanks (under 40 litres): Small volumes of water change quickly. Start with changing 20% of water every week and adjust up or down as needed.
- Community Planted Tanks (100-200 litres): This is going to be the most forgiving setup for beginner moderate maintenance. Start with changing 25% of your water every two weeks. Evaluate after one month to see if this is enough or too much.
- High-Tech Tanks Using CO2 Injection: These tanks require weekly water changes regardless of size. EI style methods using large water changes every week are preferred because it works with your fertilization regime to provide a weekly nutrient reset.
- Low-Tech Walstad Style Setups: Many aquasoils will release nutrients into your aquarium over long periods of time. Many aquarists report being able to get away with performing monthly water changes of 20-30% after their aquarium has fully cycled and established itself (usually takes 8-12 weeks).
- Breeding setups: You may need to increase changes more than you think. Because breeders often have a higher bioload from fry and feedings you may need to increase your normal water change schedule by approximately 50%
- Quarantine and hospital tanks: If you set up your qt or hospital tank without any plants you will need to change water daily or every other day. 20-30% of volume is still appropriate though.
Benefits of Understanding Water Changes
- Steady reliable plant growth. Your plants will not experience the boom and bust cycle of growth that occurs when nutrients are allowed to fluctuate week to week.
- Less Algae. Nutrient dilution from regular water changes helps limit the total amount of dissolved organic carbon available for algae to utilise.
- Healthier Fish. Stable water parameters mean less stress on your fish which leads to fewer slime coats and happier fish.
- Savings. By only changing enough water to keep your aquarium running optimally you won’t be wasting money on excess dechlorinator.
- Time management. If you know how much you actually need to change you can plan your day around water changes rather than trying to cram it into whatever free time you may have.
- Longevity. A well maintained aquarium that doesn’t change too much or too little water should go years without experiencing a total crash.
Setting Yourself Up for Success
Phase 1: Setup & Baseline
The first thing you need to do is take a hard look at your aquarium and be completely honest with yourself. How heavily planted is it really? Are your plants growing fast or slow? How heavy is your fish bioload? These are important questions you should ask yourself before proceeding.
Grab a pen and paper and test your water parameters. Get a baseline reading for pH, hardness, nitrates and phosphates. All of these values should help determine if you are currently changing enough water or not.
For the first month go by the rule of 20% per week. If you have an obvious high bioload tank or extremely low planted density adjust this amount up or down but start with 20%.
Keep a log of what your water parameters are before and after each water change. Being able to look back on a log will help you troubleshoot any future problems that may occur.
Budget
You should already have most of the equipment you need but here is a basic rundown of costs if you need to purchase anything.
- Basic test kit (pH, ammonia, nitrite, nitrate) – £15-25
- Gravel vacuum – £10-15
- One months supply of dechlorinator – £8-12
Estimated starting budget £35-£50
Phase 2: Observation & Adjustment
During the second month you should start to get a pretty good idea if your previous water change schedule was too much or too little. Ideally your nitrates will begin to stabilise and hover between 5-20ppm. If your nitrates stay consistently over 20ppm your last schedule was too slow. Add another water change per month or increase the amount of water you change at each session.
If your aquarium stays consistently under 5ppm and your plants are showing signs of nutrient deficiencies you can probably cut back on water changes.
Pay attention to how your plants are growing as well as how your fish are behaving. Healthy fish that aren’t hiding all the time and plants that show new growth every week are signs that you have your water changes dialed in just right.
If your water changes require you to significantly adjust your tanks temperature you should look into a way to decrease temperature fluctuations. UK tap water can range from anywhere around 6°C in the middle of January to 18°C in July. This can cause a huge problem when doing water changes during these extreme seasons.
Budget
Here is a basic list of additional items you may need to purchase during month 2 of setup.
- Additional test kit reagents – £5-8
- Thermometer used for mixing new water – £3-5
Additional budget £8-15 should be enough.
Phase 3: Striving for Perfection
You have now gone 4-6 weeks monitoring your aquarium and adjusting water changes as necessary. It is now time to sit down and figure out what your ideal water change schedule will be. By now you should have figured out exactly how much water you need to change to keep your aquarium looking and running the way you want it to.
Write down what day of the week you will change water, how much you will change and any seasonal adjustments you need to make.
Plan your day around your water changes. If you know that every Sunday is water change day you can schedule everything else around that. It is a lot easier to keep up with a routine like that then say “Oh I haven’t changed my aquarium water in a month” because you can’t find the time.
Remember to take seasons into consideration if you live in the UK. Winter water changes will be trickier and you may need to reduce the amount you change at one time.
Summer water changes are much easier but you may experience more issues with chloramines requiring you to use more dechlorinator.
Budget
You have now accumulated all the tools you need and can probably use things you already own to meet this months budget.
- Long term supply of dechlorinator – £20-£30
- Speed affordable upgrades to your maintenance tools. Better siphon maybe? – £15-25
Additional budget £35-£55 should cover this month.
Phase 4: Maintenance
By now you should have established a permanent water change schedule that you know works with your aquarium. Once every quarter (every 3 months) you should sit down and verify that your water changes are still appropriate.
Plant growth will naturally slow down and speeds up throughout the year. You may find that during summer you need to change water slightly more because your fish eat more food during warmer months which increases the bioload.
You should periodically cheque for slow declines in water parameters. pH, hardness and other parameter can slowly change over months without you noticing. Regular maintence will minimise these occurrences.
Look for any major lifecycle changes that may require you to change your water more or less. A huge trim of your aquarium plants may require you to increase water changes temporarily until they regrow.
Monthly budget
You should be all setup by now. A quick £15-25 should be enough for water treatment additives each month.
As you can see there is no definite answer when it comes to water changes in planted tanks. By taking the time to properly setup and maintain a testing regiment you can customize your water changes to your aquariums individual needs.<|end_of_document|>
