Fish Tank Guides Maintenance and cleaning

The 5 Secrets to Crystal Clear Aquarium Water

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The secret to crystal clear aquarium water

Want to Know the Secret to Clear Aquarium Water?

This post is poorly titled, as I can tell you that the route to having crystal clear water in your aquarium is no secret. Having crystal clear aquarium water is achieved by using good quality, appropriate equipment and a bit of elbow grease.  Ultimately it all comes down to good filtration and a good maintenance routine.  There are, however, a few extras that can help you out if you’re still struggling.

Through this article, we’ll cover the basics of making your aquarium crystal clear, plus the extras that can help you along the way.  By the end of this short article, you will have all the tools you need to have the clearest water possible in your tank.


Why Is My Water Murky?

The Cause

If your aquarium water is not clear, it’s quite important to know why.  If you know what is causing your murky water, then it’s easier to fix:

If your water is green, your problem is likely algae – Learn more on algae here 

If it looks cloudy then it’s a bacteria issue.  If you have a bacterial bloom, this usually means that there is an imbalance in your aquarium and one type of bacteria is multiplying uncontrollably.  This issue will usually resolve itself in time.  But in the meantime, water changes will help to control it.

If it looks yellow/brown, then you have likely added tannins to your water from a new piece of wood as decoration.

If it looks hazy then the cause is likely dissolved inorganic compounds, such as phosphates.


Now It’s Clear, Let’s Keep It that Way


The first and most important route to crystal clear water is a good maintenance routine.  That means water changes.  This is something that every aquarium keeper has to do and there is no avoiding it.  This is because nitrates build up in your aquarium as ammonia is converted into nitrite, which is converted into nitrate by your filter.  Plants use this nitrate as food, and algae are no different.

This can mean that instead of nice clear water, you have green water that is filled with algae.  So removing that nitrate regularly is important to prevent these algae from occurring in the first place.

Whilst you’re doing water changes, its also important to remove any dirt, debris or uneaten food from the aquarium.  The problem here speaks for itself really, anything floating around in your aquarium is going to prevent it from being crystal clear.  If we remove it, the problem is gone.

Overfeeding your fish can also aid algae in taking over your water.  If food is left to break down in your aquarium then it releases phosphates into the water.  Phosphates are another food for algae and they will thrive on it.  So make sure any uneaten food is removed during your weekly maintenance.



Joint top on the importance list here is filtration.  Your filter needs to be powerful enough to sustain your aquarium.  It needs to be able to remove debris from the water whilst converting waste into less harmful substances to keep your fish healthy.  For me, a filter that cycles the aquarium through at least 5 times an hour is essential, but 10 times an hour is better.

Whilst this seems like a lot, most fish come from rivers, which flow much faster than that so they won’t struggle.  The only place this isn’t effective is with fish such as Betta, which requires slower flow.  Ultimately you cannot over filter, but if your fish are being blasted around the tank uncontrollably, then the flow may be a bit too high.

To enable your aquarium to remain crystal clear, your filter also needs to be well established.  By that I don’t mean that it has been running a long time necessarily, it just needs to be correctly cycled and full of bacteria (Biological filtration).  Having a good bacteria colony living in your filter means that waste is dealt with efficiently which keeps your fishy friends happy and your water clean.  This will also help to prevent an imbalance in your aquarium, which means no bacterial blooms.

Your filtration needs to be equipped to filter particulates from the water (Mechanical filtration), this is usually achieved with a sponge layer of filtration or filter wool/floss.  Using finer filter pads will catch smaller particles, meaning your water will be extra clear from any debris.

aquarium filtration




I’ve mentioned already that plants use nitrates and phosphates as food.  Having plants in your aquarium will mean that they use it.  This means that algae cannot form as the plants are already there to consume the food before the algae can.  Plants are great for assisting in cleaning your water and also add to the look of your aquarium.  Whilst having plants won’t prevent an algae bloom completely, they will certainly help, and if they are kept healthy then they shouldn’t make too much mess losing leaves etc.

aquarium plant clear water



Chemical filtration

Chemical filtration such as activated carbon can assist in keeping your water clear.  Activated carbons bind inorganic compounds that have dissolved in your water, this aids in keeping it clear.  An added bonus is that it will also help to prevent your aquarium from producing any nasty smells.

Some filtration media will also remove tannins from your water if you wish.  Tannins come from wood and a new piece of decorative wood can leach tannins into your aquarium for months.  Tannins are harmless to the inhabitants of your aquarium and in some cases are good for them.

Tannins can soften the water and lower the pH.  They do however make your water yellow/brown and murky.  This is a look desired by many aquarists, but if it isn’t for you then add some purigen to your filter, purigen works as both a bio and chemical media, it will absorb tannins overnight if you use enough of it.



Having your lighting on too long is another way to encourage algae growth.  Algae, like plants, can produce food from photosynthesis, so too much light means extra food for algae.  If your aquarium is planted, then the plants require light too, so if you’re also having algae issues, then reduce the lighting by an hour a day at a time until you find a balance.


Additional products

Discarding any that I have mentioned above, I don’t particularly recommend any other products for clearing up your water.  There are many on offer which will tell you that they will give you instant crystal clear water, and whilst some of them work, they only mask the issue.

If your water is not clear then it is likely caused by one of the issues above.  Dealing with that issue is the best way to crystal clear water, otherwise, you will be adding chemicals to your aquarium constantly, likely causing new issues, and not to mention hurting your wallet buying them.



Send us in some photos of your crystal clear water by using #seriouslyfishyclub

About the author

James @Seriously Fishy

I am a fish keeping enthusiast with over 20 years experience. I currently keep American Cichlids (CA) which are my favourite fish to keep so far. I started Seriously Fishy as I noticed a large volume of people on various web pages looking for help with Aquarium basics. I created the first Seriously Fishy book to solve the issue in 28 pages, that led to the Seriously Fishy UK fish forum and blog.

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