Common Problems And Solutions For Freshwater Aquariums

When it comes to aquariums problems are inevitable. Old or new, big or small- it doesn’t matter. Problems will appear. Finding the cause and fixing it before things get out of hand is key to long term success. They also present a good opportunity to learn a little more about how your aquarium functions and how to keep it healthier in the future.

The majority of problems ultimately boil down to an issue with water quality. This isn’t surprising, as the water is pretty much the most important part of a successful aquarium setup. Nonetheless, just what exactly is wrong with the water can differ greatly from one problem to the next. Here are a few of the most common.


Simply put, algae is going to happen. Every tank, even healthy ones, has at least some algae growth. Keeping your tank algae free is not the goal but rather keeping the algae in check. The easiest way to do this is to control the two things the algae needs- light and food. Avoiding overfeeding and blocking direct sunlight from reaching the tank will go a long way towards preventing excess algae growth.

Similarly, eliminating problem algae that has already taken hold is a matter of reducing the light and nutrients available to the algae. Lighting can be reduced to just a few hours a day and feedings can be cut back to only every other day until the algae begins to recede. Physically removing as much as possible along with a good gravel vacuuming and water change will also help cut off its source of food. Introducing some competition is another option- either algae eating fish and/or snails to directly remove it or live plants to compete for resources. Finally, if even after your best efforts the algae refuses to go away, you may want to test your water source. Algae feeds on phosphates and nitrates which are present in some water supplies.


Cloudy or Green Water
A common occurrence in new tanks, cloudiness can be the result of a couple different situations that require different courses of action to rectify.

Fine Particulates- In a newly set up aquarium, fine particles from the substrate often cloud the water. It’s nothing to worry about as they will settle out or be caught by the filter within a few days at most.

Dissolved Minerals- Cloudiness can result if the source water the tank is filled with is particularly high in dissolved minerals and/or heavy metals. A simple way to check if this is the case is to test the pH- it will be high. If this is the case a special water conditioner can be used to lower the pH and precipitate out the excess minerals. Finding a purer source of water is another option. Take caution that you don’t adjust the pH too fast if the tank already has any life in it, however. The cloudiness isn’t dangerous to the fish, but a large pH swing is.

Bacterial Bloom- A bacterial bloom is fairly common in a new tank, but can occur at any time. Typically the culprit is some source of nutrients from overfeeding, decaying plants or fish, or a general lack of maintenance. Whatever the cause, the key is to remove the bacteria’s food source. With reduced feeding and a water change or two the cloudiness will clear up in a week or so.

Green Water- As you’ve probably guessed, green water is due to free floating algae growth. The causes and solutions to this problem are much the same as with a bacterial bloom with one additional consideration- light. Algae needs light and too much of it can lead to excess growth. To treat green water, reduce the light, cut back on feedings, and perform a water change.


“New Tank Syndrome”
So common it has its own name! All too often someone new to the hobby will set up their first tank, add in some fish, then watch helplessly as those fish perish over the following days or weeks. You see, what they didn’t realize beforehand is that there is more to keeping an healthy aquarium than changing the occasional filter cartridge. The real powerhouse of every aquarium’s filtration is bacteria. It is bacteria that break down the fish’s waste from highly toxic ammonia to less toxic nitrite and finally to relatively harmless nitrate. Without these bacteria, the fish are quickly poisoned by their own waste. Luckily, cultivating these bacteria is easy, once you know how. The process is called cycling and is necessary for every aquarium.


Some fish are known and even prized for their ill temper, but even those known for their peaceful demeanor can show signs of aggression from time to time. The causes are many but it usually comes down to the fish being unhappy with something in his surroundings. Possible causes include:

•too little room
•too small of or no school (for schooling fish)
•a gender imbalance- males often compete for females’ attention; too many males and not enough females can mean problems.
•incompatibly of species- unrelated species with similar appearances, fin nippers housed with fish with delicate flowing fins, etc.
•aggressive individuals- some individual fish are simply more aggressive than others

Many aggression problems can be fixed simply by adding or removing fish to alleviate the issue. Removing the bully rather than the victim is preferable. Furthermore, temporarily isolating problem fish or rearranging the tanks decorations as well as adding to them will sometimes work.


Ammonia Spikes
Just as ammonia can be a problem in a new tank before a bacterial colony is established, so too can it be a problem in an established tank should its balance be thrown off either by a new source of ammonia or a loss of beneficial bacteria that process it. Excess ammonia production often comes as a result of something rotting within the tank. This could be a dead fish or plant, or a clogged filter, or just lots and lots of waste collecting in the gravel. On the flip side, bacteria can be lost due to overzealous cleaning. The beneficial bacteria live on pretty much every available surface in the tank including things like the gravel, any decorations, and of course inside the filter. Removing any of these items from the tank for a wash with tap water or any cleaning product is a bad idea as it will likely kill much if not all of the beneficial bacteria.

In either event, the goal is to manage the ammonia until the bacteria can readjust to handle it. If the tank has fish living it it during this time the ammonia level will need to be managed with water changes and monitored closely while the bacteria rebuild themselves. Feeding should be suspended temporarily as it will only put more stress (in the form of waste) on the system. Finally, heavy aeration can help dissipate the ammonia somewhat.


PH Problems
If there were one word to describe a healthy aquarium it would be stability. A stable temperature, stable filtration, and a stable pH. Knowing this it comes as no surprise that keeping the pH stable is much more important than matching the exact recommended pH for your fish and if they seem healthy and the pH is stable then adjusting the pH isn’t recommended. However, should you find your pH is particularly far outside of the desired range (possibly as a result of the source water) then there are a few methods you can use to adjust it. Just remember to go slow if the tank already contains fish.

Add these to the filter a little at a time to adjust the pH in small increments, allowing it to stabilize before adding more:
Lower pH- peat moss
Raise pH- crushed coral

Another option should you find the problem is your source water is using either distilled or RO water, which will both have a neutral pH of around 7. These can be mixed with the source water to bring its pH closer to 7, whether that be up or down. Finally, commercial products for raising or lowering the pH should be avoided- they’re more suited for one time fixes and would need to be continuously added to have a lasting effect.


Oily Film On Water Surface
Oily substances can make their way into your tank in a number of ways. Fish food is probably the number one source as it often contains some amount of fats and oils. Oils from your own skin or any lotions or other skin care products you use can also get left behind during maintenance. They can also drift in from the kitchen. Have you ever noticed that fine layer of oily greasy gunk that builds up on kitchen surfaces? Some it can find its way to your tank. Fish waste as well as dead fish can also release some oil as they break down. Finally, damaged equipment could release some oily substances.

Whatever the source, the oil itself likely isn’t all that harmful (with the exception of those from skin care products– care should be taken to never get them in the tank). But, it can impede gas exchange which can throw off the tank’s balance and make it harder for your fish to breath. The first step of course should be to determine the source and cut off the supply. As for removing the oily film, a paper towel can be gently laid on the surface of the water to soak it up with the filter and anything else that will cause turbulence turned off. Alternatively, the surface water can be skimmed away during a water change taking the oil with it.


Fish Gasping At Surface
This could be one of two problems- low oxygen or high ammonia. If ammonia is the issue the tank may not be cycled or the bacterial colony that processes it may have been damaged, see above to fix. As for low oxygen, increase surface agitation and/or add an air pump with an air stone.


Temperature Problems
If your tank is located somewhere that the temperature can fluctuate from day to day then you may eventually run into problems keeping it steady. A heater is of course the easiest way to keep the tank from getting too cold. If the tank is in an unheated room during the winter additional heaters or a larger heater may be necessary. Some sort of insulation, like a blanket, can also be wrapped around the tank as a temporary fix, such as during a power outage. However, most heat is lost at the water’s surface so this will only help slightly.

As for keeping the aquarium from getting too hot there are a couple options. A chiller is one of them, but, being as they’re often quite expensive, is a bit extreme if your tank’s temperature only occasionally creeps a bit too high. A more practical option is simply turning off the lights on those especially hot days. The lights contribute a lot of heat to the tank as well as the room it’s in. Increasing evaporation is also a good way to cool the tank. Opening the lid and positioning a fan to blow across the water’s surface can drop the temperature by several degrees. It may seem like a solid idea, but using ice isn’t generally recommended. It can cause serious harm to fish or plants that it comes in contact with and ultimately isn’t very effective as it takes a lot of ice to cool the water and the effect isn’t long lasting.


High Nitrates
Steadily climbing nitrate levels really are the goal of most healthy aquariums. After all, they’re the end product of the nitrogen cycle you worked so hard to complete. Of course, that doesn’t mean they’re a good thing- just less bad than the alternatives. And while there are bacteria that consume nitrate and convert it to free nitrogen gas they’re quite difficult to culture in the average home aquarium. This means that, without some sort of intervention, the nitrate level will eventually become a problem. So what’s the simplest and most effective way to reduce the nitrate level? Water change. Like oh so many problems the easiest solution is to just change out some of that old dirty water for some fresh clean stuff.


A theme appears when it comes to fixing these common problems- water changes. The vast majority of problems can be fixed or at least alleviated simply by changing a bit of water. Furthermore, regular maintenance is key to preventing problems from occurring in the first place. Finally, even if things seem to be going well, conducting a few simple tests every now and then will go a long way towards ensuring a happy and healthy aquarium.

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