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Cloudy Aquarium water - Causes and Solutions

Updated: Apr 24, 2020

Cloudy water. Is it something to do with temperature? Is it bacteria? Is the light too strong? Cloudy water can be confusing for many aquarium owners and unfortunately, there’s isn’t a direct answer or a singular cause. That’s not to say we can’t try and narrow it down though, which is what this article is about! So, if your water’s turning grey, have no fear! Let’s dig in and see how you can fix it!

Grey or White Water

Firstly, this could be your gravel. Has it turned grey a few hours after setting up your tank? It could be that you haven’t rinsed the gravel enough. If you’ve put your fish in already (which you shouldn’t have, ALWAYS cycle your tanks for at least a week before adding fish! Learn more about that here) then it’ll be a little more difficult. Scoop some water out of your tank and put it into a bucket or large container, then scoop out your fish and keep them in a safe spot while you tend to the tank. You could also opt for a Gravel Vac to try and clean it - these will also come in handy in the future when you'd conducting water changes. They come in powered and none-powered versions. See below for an example).

Now that the tank is empty of fish life, start emptying as much of the water as you can. Take out your ornaments and equipment if it’s relatively easy to do so, and start adding a couple of inches of water into the tank. Using your hands, swirl the water and gravel around - the dirt should rise to the top of the gravel so that you can pour it out easily. Empty the water again and repeat the step. Go over it a few times until the water remains clear. Then you can start assembling the tank again - obviously leave the fish til last but get them back into their home as soon as the tank is ready for them. If they’re usually based in warm water, get your heater on, or you can boil a pan of water or a kettle to give the temperature a boost too. Make sure you don't clean out your filter at this point. The tank cycling process depends fully on good bacteria being present in your tank, and a lot of this bacteria is housed in your gravel, but a lot is also in your filter. When you clean the gravel, you essentially remove a lot of this good bacteria and you'll get some spikes in your tests for a while until the bacteria in your filter grows out into the gravel.

If that doesn’t solve the issue, it could be the water itself - if you’ve filled it from a tap then it could contain heavy metals or phosphates and silicates. If this is the case, testing the water will show you this and the pH level should be more towards the alkaline side. If you’ve got a positive diagnosis for this, then you can buy water conditioners that can resolve the problem.

For water conditioners we can really only fully recommend two products, and that's Tetra Aquasafe or Seachem Prime. We only recommend these products because they're the ones that we all use here at Your Pet Guides, they have excellent reviews and we've never had any issues with them. In future you’ll have to opt for either RO water (Reverse osmosis water), available from lots of aquarium shops, or distilled water, but go easy on the distilled water - a small tank full of it can harm your fish. It’s good to keep it balanced.

If your tanks been set up for a while and the white/grey water’s been more of a slowly approaching issue, then that could be a bacterial issue. As the new aquarium goes through the initial break-in cycle, it is not unusual for the water to become cloudy or at least a little hazy. It will take several weeks to several months to establish bacterial colonies that can clear waste from the water which is why we suggest cycling your tank for up to 8 weeks unless you have bacterial colonies from other tanks. Over time, that cloudiness will resolve itself. Decaying plants or excess food that remains uneaten can also cause the milky water seen in bacterial bloom.

You can add snails to your tank if you want to take care of this, but don’t add too many because when they breed, they breeeed. Nerite snails however, don't reproduce in aquariums and are one of the best options for algae eaters - read more here.

Another option for bacterial bloom is to do a water change, try about 30-40% and see how the water looks after. You can keep it in check by removing decaying plants and uneaten food then vacuuming the gravel every now and then. If you’re over feeding then cut back on the food delivery schedule to every second or third day. Also make sure to check your filter is performing okay - it might need a clean.

You can test your aquarium water with specialized test kits. There's only one product we'll fully recommend here and that's API's range of test kits and strips, they're one of the biggest names with this area of products and the strips are available at a wide range of prices. We'd opt for the master test kit though, it's a little more expensive but will last 4 times as long and it's more accurate!

On to Green Water - It’s algae. Next!

Okay, if it’s green, it can really only be algae, diagnosing it is the easy part. Possible causes include too much light, too many nutrients, too many phosphates, or too many nitrates.

Too much light is typically the easiest to fix - if your tank is next to a window, it needs to be relocated. If it’s not next to a window, try keeping the lights off for longer periods. Both of these will reduce algae growth. You could also buy a new tank mate that will eat the algae, such as some snails like Nerite Snails, Pleco fish, Mollies or, as the name suggests, a siamese algae eater.

Helpful article for an algae problem: The Best Algae Eaters for Freshwater Tanks

Too many nutrients is harder to fix as you need to work out why it’s there. A water change will give some quick relief but isn’t going to fix it. Grab a water testing kit and see what the results are - the packaging should direct you to which action you need to take.

Too many phosphates is relatively easy - it’s either coming from excess food or the water source itself. Test your water source for high levels of phosphate - if this is the issue then you’ll have to use RO water or get a phosphate remover to treat the water. If the feeding is the issue, reduce the amount of food you give, and consider looking for an alternative brand that has lower phosphates in.

Nitrates, they naturally rise in the aquarium over time as a byproduct of fish wastes. The only way to remove them quickly is to perform a water change. Make sure your filter is kept clean and is adequate for your tank size as this will slow the rise down. Also, make sure you have not overstocked your aquarium, or you will constantly battle rising nitrate levels. For every 1 inch you have of fish, you need around 3-5 gallons of water (13L to 22L) to keep maintenance at an acceptable rate. To combat nitrates at a slower, but passive pace, invest in live plants. They'll remove nitrates and nitrites, whilst also adding oxygen to your tank. We recommend Java Fern as a first live plant, as it fits well with most fish because it doesn't taste too great, so your fish wont just nibble it before it can help your tank water parameters.

Thanks for checking out this Fish Article! Here's a list of our other popular articles:

How To Set Up Your First Aquarium

Common Care Mistakes in First Time Fish Owners

The Beginner's Guide to Planted Tanks

The Minimal Maintenance Aquarium Set Up Guide

How To Clean Your Aquarium and Decorations

How To Spot Illnesses in Fish

Clean Up Crews for your Freshwater Aquarium

The Best Algae Eaters for Freshwater Tanks

The Best Aquarium Invertebrates

The Ultimate Guide to Setting up and Cycling your Fish Tank

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