Cloudy water in an aquarium - Causes and how to deal with it

One of the most common problems aquarists have to deal with is cloudy water. Whether we are talking brand new set ups, tanks cycled tanks running for a few weeks or established mature tanks at some time or another I have keepers asking me why this has happened.

Hopefully this article will explain a few of the reasons, how to combat the problem, and how to prevent future occurrences of this problem.

New set ups:

We have just arrived home with our brand new tank, gravel or sand, and some nice shiny ornaments. Everything has been put in the tank and the water has clouded up.

One cause of the cloudiness could be part of the cycling process as the tank water will be unbalanced, but when the cycling is complete it should clear itself, but more of that later.

A must when setting up the tank is to rinse thoroughly the gravel or sand being added as if this isn’t done it will create cloudiness when the water is added. Not the nicest of jobs, but necessary. Add the substrate to a bucket, cover with clean water, give a good swirl & empty the murky water. Repeat this process till only clean water is in the bucket, now the substrate can be added.

The ornaments must be aquarium safe; if not they can leach toxins etc. into the water. Always rinse these before adding them to remove any alien coatings or debris on them. Bogwood etc. will release tannins into the water unless it is are pre-soaked for a couple of days, changing the water as you go. The tannins will give the water a yellowy appearance.

As these tannins are acidic in nature these will also affect your pH therefore giving an unnatural balance.

The water in cycling tanks undergoes a lot of changes so at some stage it will be probable that cloudiness will occur, once the cycle is complete the water will clear itself, in some case this can happen overnight.

Cycled tanks:

Our tank has now cycled, been running for a few weeks, we have added fish, plant etc. but for no reason the water has gone murky. This could be due to decaying plant matter, overstocking the tank, over feeding the fish. The reason for the murkiness will most likely be a bacterial bloom caused by the factors mentioned. Another reason could be nitrates, phosphates being added into the tank on water changes, test your water and if this is the case then a water purifier like an HMA filter or an RO filter might be needed to keep your tank water clean.

If keeping plants look for leaves rotting, remove them before they foul the water. The general rule for stocking fish is one inch per gallon of water, go over this and your filtration system may not cope, therefore it will not remove the bacteria from the water effectively.

Fish only have small stomachs, it is better to feed small amounts 2 to 3 times per day, rather than one large meal. Any uneaten food should be removed from the tank if possible, try to clean the surface of the substrate on a regular basis with a gravel cleaner etc., occasionally remove the ornaments for a clean.

Do regular water changes, remember small regular changes are more beneficial to keeping your water stable, rather than large ones done every now and again (I do 10% changes weekly). All of this will help to prevent bacterial blooms in your tank. I have mentioned nitrates & phosphates; these can give you green water as well as incorrect tank placement, leaving the lights on for too long a period.

Green water is caused by algae being present, you may need to add phosphate/nitrate remover to your system to combat this, eliminating the algae food source, or even restrict feeding the fish to every other day. Check the food you are giving to the fish as some actually have phosphates in them so change the brand you are using.

Is your tank place in direct sunlight for part of the day, how long do you leave your lights on for? Sunlight will promote algal growth as will the lighting. Lights should never be run for more than 12 hours and if you are running them for less try reducing the time even more to clear the water.

Keep you filtration system clean, don’t let it get clogged.

If suspended particles are causing the discolouration try adding filter wool to your filter to trap them, but this will need replacing on a regular basis.

Nitrates over a period of time will rise in your water; the only way to reduce them is by regular water changes.

There are several additives that are available to add to your system for water clarity, these are known as flocculants. they work by clumping the suspended debris together, which then allows the filtration to pull them out of the system.

But remember, these are only a short term solution to the problem; in fact overuse of these can create more problems by altering the balance of your water.

Cloudiness can also be caused by fine air bubbles in the suspended in the water, normally after water changes, these should disappear in a couple of hours.

To summarise keep your tank and equipment clean, do regular water changes, don’t overfeed the fish, and do not overstock your tank.

Follow these rules and you should have a thriving set up with superb water clarity.