How to Fix Your Cloudy, Milky Fish Tank

By Eddie Waithaka @aquariawise

Why Your Aquarium is Milky White (+Solutuons)

The idea of an aquarium is to enjoy your fish, but you’ll very likely experience a problem with water clarity at least once.

Usually, a milky white tank is a result of varying factors, either of which or all may manifest in your tank.

The cloudiness is caused by residue from poorly cleaned aquarium gravel or dissolved mineral constituents, but by far the main cause is bacterial bloom especially in new tanks.

As ammonia from fish waste builds up, bacteria start to establish and float through the water creating the cloudy appearance.

There are a few chemicals available in the market to help clarify a cloudy fish tank, though the quick and most effective solution is to deal with the cause, plus maintain your entire aquarium in top condition.

That said, let’s dig a little deeper into the causes and solutions for cloudiness in fish tanks.

Why Your Aquarium has White Cloudy Water

As mentioned, a hazy tank is a result of varying reasons.

These are the 3 major causes:

Gravel Residue

Washing gravel before adding it to your tank helps remove specks of dirt and dust which would otherwise dissolve in the water.

So, if your water turns cloudy a few hours after adding new gravel, there is a chance you didn’t wash the gravel properly, or you forgot to wash it altogether.

The washing process should generally take less than 30minutes.

But in case you’ve already added the gravel in your tank, don’t panic. Simply drain the fish tank, then wash and rinse the gravel until the water runs clear.

After that, put back the gravel and refill your tank.

Bacteria Blossom

If you’ve cleaned your gravel properly but the white haze remains, you may be looking at bacteria bloom, which vaguely means bacteria from your aquarium bio-filter are settling.

These are the nitrifying bacteria used to make the water safe for fish by converting highly toxic ammonia produced by organic matter to the less toxic nitrate.

Realistically, a single bacteria would not be visible, but when they accumulate they become quite conspicuous.

Mostly, bacteria bloom will mostly manifest after cycling a new aquarium, which means haze won’t establish once you add your filter, instead, it’ll appear a few days or weeks later; when the bacteria start to colonize your tank.

However, cloudy water in the fish tanks might also be a result of unfiltered food and plant residue before the biological filter elements adapt to your tank’s environment.

If indeed the cloudy water is caused by bacteria bloom, the situation should resolve itself within a short time. It’s, however, crucial to do a weekly water change to remove any residual dirt sitting in the tank as the filter acclimates.

Plus don’t overfeed your fish and generally try to cut back on the feeding to keep down dirt from uneaten foods.

Dissolved Substance

Both water and substrates contain considerable amounts of phosphates, nitrates, silicate, and other minerals which may leach and turn your water cloudy as well.

Silicates are especially high in sand substrates like blasting sand. Plus tap water contains all three compounds which breakdown and release into your aquarium.

Apart from the milky haze, nitrates, phosphates, and silicates in domestic water may cause other problems. For instance, silicates and nitrates promote the growth of brown algae (diatoms), whereas all three mineral feed green algae.

To solve this problem, get your tap water tested for mineral content or use a pH kit to do the test yourself. Conventionally, mineral-rich aquarium water will have a high pH, which you can easily resolve by adding a conditioner.

Another solution is to use RO water.

But, RO water is too pure for aquarium use, so add remineralizing additives to ensure you only get allowable amounts of minerals in your tank.

What about Green Cloudy Fish Tank?

Sometime, the haze in your water will be green instead of milky white, despite both problems are equally unsettling.

So, what causes green-cloudy water in a fish tank?

Unlike white-hazy water which is caused by a myriad of reasons, green-cloudy water is easy to pin down, but a lasting solution is a little harder to come by.

Basically, a green haze in your fish tank is entirely caused by algae overgrowth.

Hence, understanding what causes green algae growth, is the first step towards a solution.

#1— Excess Light

Too much light in your aquarium, whether natural or artificial will sprout green algae, so keep your lights on for a reasonable period to definitively deal with the menace.

I recommend switching off aquarium lights after 12 hours or move the tank away from the sunny spot if the light from the sun is causing the overgrowth.

Ideally, 12 hours of light are sufficient even for planted aquariums to thrive, with your plants and fish resting the rest of the day in darkness.

However, the situation is often a catch 22 because, depending on the intensity of your lights, even 12 hours could be enough for algae to thrive. Ergo combine this hack with others chops like adding algae eaters in your fish tank.

#2— Excess Nutrients

Minerals in your aquarium will provide sufficient nutrition for green algae, and in low light, brown algae, these nutritious compounds include phosphates, nitrates, and silicates.

A water change will give some immediate relief, but won’t resolve the issue completely. It’s, therefore, better to deal with the compounds from the source.

Use remineralized RO water as an alternative to tap water which will generally have excess minerals.

A thing to note though, nitrates in an aquarium are mostly a by-product of fish waste and the only way to keep the levels in check is through frequent water changes.

Moreover, adding live plants in your fish tank will go a long way towards keeping the nutrient levels down. Go for fast-growing aquariums plants as they use up the minerals readily.

How to Fix a Cloudy Fish Tank

Cloudy aquarium water is an issue that a lot of fish tank owners face. Luckily, there are many solutions to this problem, many of which show quick results.

Here are the most effective ones:

Focus on Your Filter: Add Activated Carbon Media

Hazy water caused by bacteria bloom will clear out with time. However, add activated carbon media to your filter, to help adsorb the nutrients that feed the bacteria bloom, and clear the water quickly.

Also, consider the overall strength of your filter since only a good unit will adequately clean the cloudy water. With the wrong filter, your aquarium will remain hazy long after the new tank syndrome has passed.

In addition, it is important to clean your filter pads regularly seeing that clogged filters media don’t operate efficiently, hence not effective at cleaning cloudy water.

Use an Aquarium Water Clarifier

Water clarifiers are designed to clump floating hazy particles together and make them large enough to be trapped by your mechanical filter.

Alternatively, they’ll drop to the bottom of the tank where you can easily siphon them from the substrate.

A good clarifier should also remove any other unsightly particles in the water such as uneaten fish food, dust, and other debris.

However, make sure it’s rated for use in freshwater tanks and won’t harm your fish, plant or inverts if any.

Moreover, use a clarifier to clear your aquarium once you’ve identified and dealt with the source of the cloudy haze.

Do Regular Water Changes

Since fish waste, excess food, and other organic materials still breakdown into toxic compounds even as your filter bacteria adapt to the tank environment. Frequent water changes are paramount to eliminate this waste.

These changes and other remedies will temporarily clear your water before the bacteria bloom is complete. Plus changing the water and cleaning your tank is the only way to remove dissolved nitrates and phosphorus.

I recommend changing at least a third of the water once a week when busy and two times whenever you get a slot.

Clean Your Substrate Properly

Make sure you clean new gravel before you install it in your tank. This will remove the little unseen specks of dirt that launch into your water when uncleaned pebbles rub together.

Alternatively, if you have another healthy well-established fish tank, add a few handfuls of gravel from that aquarium to seed developed bacteria which will speed up the clearing process.

When dealing with an already installed substrate, use a siphon vacuum gravel cleaner to remove the dirt. Debris in the gravel is pulled away with flowing water and disposed of while pebbles fall back to the bottom of the aquarium.

Cut Down On Feeding (+ don’t Overfeed Your Fish)

Very few nitrifying bacteria will properly break down uneaten food in your tank. Which is unfortunate considering it’s a major source of dirt in any aquarium.

So, this solution should be quite straight forward. Ironically, most new aquarists fail to adopt it because they fear to starve their fish.

However, contrary to common belief, fish can go a couple of days without food. In fact, a lot of food go to waste if you are used to feeding your fish more than two times a day.

Granted, cut down the feeding to one time each day or even every other day.

This will let the bacteria bloom slowly without causing excess cloudiness in your tank. Plus nitrates and phosphate levels will remain and only form minimal haze.

Don’t Add Too Many Fish in Your Tank

More fish produce more waste, which also means more nitrates and thicker hazy in your water and with more ammonia, the nitrifying bacteria will bloom rapidly which in turn make your tank cloudy.

Granted, each fish should have at least 5 gallons of water to itself and 10 gallons for bigger species like Oscar fish.

Plus consider the species of fish you keep.

For instance, goldfish will produce a lot of waste compared to betta fish which are not as messy, which means a goldfish aquarium is more likely to get cloudy.

That’s all…

…all the best and enjoy fish keeping.

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