Common Problems for New Aquarium Keepers

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As a person who’s been keeping aquariums for literal decades, it can be easy to forget how it feels to try and maintain a healthy aquarium without a firm grasp of some of the more technical aspects of aquarium husbandry. Fortunately for me, I have a seemingly endless number of novice aquarium keepers who contact me with questions about the problems they are having with their aquarium to remind of the issues that often plague new aquarium owners.

 Fortunately for me, I have a seemingly endless number of novice aquarium keepers who contact me with questions about the problems they are having with their aquarium to remind of the issues that often plague new aquarium owners.


The biggest and most common aquarium problem relates to over-feeding of the aquarium, a problem that is almost ubiquitous in aquariums. Even in the public aquariums in which I’ve worked, over-feeding fish was relatively common practice. Of course in those instances, excess foods were also removed via siphon or net at the end of each day, thus mitigating how much excess food decomposed in the aquarium water. While this may reduce the rates of waste-product build-up in the aquarium, it still leave the very serious issue of the fish over-eating, which in the long-run can lead to fatty-liver disease, an obesity-related malady that can take your fish’s life.

The solution of course is to feed in moderation. You fish obviously need enough food to keep themselves sustained, and breeding or growing, as the case may be. However, excess food allowed to sit un-eaten in the aquarium will cause excess nutrient accumulation which may contribute to excessive algae problems. Uneaten food can also harbor some pathogens, and keeping the tank free of such organic debris is a key component in keeping your fish healthy.

Excessive Lighting

Excessive light is the bugaboo of any professional aquarium maintenance service, as well as a contributor to algae problems in most home aquariums. Simply reducing how much light you put on your aquarium can have a huge impact on the aquarium’s aesthetic appearance. As such, aquarium lighting only need be switched on during the periods you are actively observing your aquarium, this of course provided that your aquarium is located in a room with windows and thus natural lighting.

A common mistake is to leave aquarium lights on for all of the waking hours of our days. It’s not uncommon for me to encounter aquariums that receive 12+ hours of artificial lighting every day, a figure that is far too long for simple aquarium maintenance.

In order to maintain healthy lifestyles, fish simply need a day and a night cycle. Most spend very little time in sunbeams in the wild, as that exposes them to predation. This means that if your fish are being a little bit more shy than you would prefer, try reducing light levels in the tank to see if your fish aren’t just being a bit shy.

Improper Temperature

A stable aquarium temperature is one of the most things you can provide for your fish in order to ensure their health, yet it is a facet of aquarium care that seems to be over-looked by many people. One such issue is the mis-management of the aquarium heater, particularly the continuous observation of that temperature with the use of an accurate thermometer.

Think about the thermostat in your home, how often do you check the temp on the thermostat each day? I’d think once or twice on average for most people, the temperature on your aquarium should be checked no less often. As much as we’d like our devices to be fool-proof and worry-free, you simply should not presume you have a stable accurate temperature…you must monitor it regularly.

Thermostats can malfunction, heaters can break, under-sized heaters can fail to keep up with the low temperatures of the cold winter months, or HVAC elements can change the temperature of an aquarium intermittently.

In an ideal world you don’t want your aquarium water temperature to fluctuate any more than a degree a day, even that would feel extreme to some species.

You can consult a quality species reference to find the appropriate temperature for your specific animals, however I recommend that you keep tropical aquarium species between 76-78F (~24-25C) at all times.

Modern Chlorine & Modern De-Chlor

Most aquarium keepers will need to address the chlorine that
is in their tap water before it can be used in their aquarium, a product added to the water to prevent microbes from taking up residence in water supply pipes.

Historically, chlorine was mitigated through carbon
filtration (very effective at removing chlorine), aeration (where chlorine is allowed to evaporate from the water), or treated with a chemical affectionately referred to as “de-chlor”, an aquarium additive used to make the toxic chlorine compound non-toxic.


In more recent times, some municipalities have started adding chloramines to their water supplies as a means of disinfection.

Chloramines are a group of chemical compounds that have both chlorine and ammonia, and are used because they are more stable in solution, and will not evaporate out of the water as traditional “old-fashioned” chlorine.

Critically, if your municipality utilizes chloramine, you cannot simply use “old-fashioned” de-chlor as your means of neutralizing chlorine as this can actually lead to a large spike in ammonia introduced into your system as a component of the chloramine. 

Unlike chlorine, chloramine cannot be removed by letting water sit out for a few days. However, products are available at aquarium supply stores that can remove chloramine. Ask your local pet store about methods of removing disinfectants from water for these pets.

Removal of chloramines is easy, you simply need modern de-chlor for the modern chloramines. There are actually a variety of products that you can use, however Prime by Seachem is the product Fish Geeks would recommend. Prime is found in most big-box pet stores as well as specialty aquarium retailers as well. Use Prime whenever you add water to your aquarium.

When Hardness Matters (and when it doesn’t)

One of my observations over my years working in the aquarium industry is that far too many people don’t understand what “hard water” actually implies. The problem could stem from the fact that there are at least two water chemistry measurements that we call hardness, and to make matters worse one type of hardness is of vital importance in aquarium husbandry, and the other is almost irrelevant. To make matters worse many people have hard water in their homes, and have water softeners or other water treatment systems in place to remove the “soften” from the water.

Confused? Don’t worry, you’re not alone.

As a first step in understanding this, let’s think about the most basic chemistry, or perhaps more importantly, where that chemistry comes from.

Our water has dissolved minerals. Those minerals come from rocks, mostly calcium carbonate or magnesium carbonate rocks, that literally dissolved in water (over many millennia), leaving behind the calcium, magnesium, and carbonate in water…these are the compounds we call “hardness”.

However, in order to be more precise (and perhaps less confusing), we should give these chemicals different names. This is why we call the calcium and magnesium in water “general hardness,” often simply termed GH. General hardness is why you would need a water softener in your home, and the calcium and magnesium are what that device is removing. For most intents and purposes, you can ignore GH in simple aquariums, and softened water is fine for most fish.

However, if you once again consider how hardness gets into water in the first place (through the dissolution of rocks), then it would follow that water high in calcium and/or magnesium would also have an elevated concentration of carbonates, the other component of those rocks.

Carbonate concentrations in your aquarium are very important, in fact they have a direct influence on your pH, the concentration of carbonates in your water is traditionally called carbonate hardness, abbreviated as KH by German-speaking aquarium keepers. However, in modern parlance we refer to carbonate levels as your “alkalinity,” because elevated levels of carbonate ions in the water generally coincide with alkaline pH levels.

Two important factors about hardness. First, water treatment facilities add compounds that will increase alkalinity without increasing general hardness. These levels can and do fluctuate throughout a year. This is why regular monitoring is necessary, especially for new aquarium keepers.

You will need to test your source water and either increase low alkalinity through the use of chemical buffers, or alternatively dilute the elevated alkalinity with reverse osmosis filtered water.

The second important factor to remember is that your system will “consume” the alkalinity as a result of the nitrogen cycle. You will need to either replenish the alkalinity through a dosing regimen, or preferably through a prudent water change routine.

Magical Potions

Speaking of water chemistry (I know, I’m almost done), no area proves to be as big a bugaboo to novice aquarium keepers as does the difficulties in maintaining a stable chemical environment. Either the pH is fluctuating, or the ammonia is too high, or nitrates are through the roof. Trust me, I’ve heard (and seen) it all.


A quick stop into any pet shop of aquarium specialty store will have a novice aquarium keeper convinced that the key is simply waiting in one of the brightly labeled bottles of aquarium products sitting prominently on the store’s shelves, and touting huge benefits.

So, what is the secret? The secret, if there is one, is that there is no ONE single thing you can do to ensure stability…what’s more, there’s no secret product, solution, or elixir that can guarantee your success.

Rather than engage in any debate about “how effective” any of these additives may be, I’ll simply assert that with proper husbandry, they are simply not necessary.

This is why I stress to many of my new clients that there is simply no chemical you can add to an aquarium that will “take things out.” Even the chemicals that we use to neutralize chlorine merely convert the chlorine compound into a less toxic compound rather than “remove” the chlorine itself.

In this sense, the best solution to a water quality issue usually involves a water change, which is why I repeat this mantra for newer clients:

The solution to pollution is dilution.

If you have a pH issue, the first step is to test your aquarium alkalinity and compare it to your source water. Provided your source water has ample alkalinity (most do, even in homes utilizing a water softener), a water change is fine solution to a low or fluctuating pH.

If you’re having algae issues, do a partial water change (and reduce lighting) a few weeks in a row. By simply reducing the levels of nutrients (usually nitrates and phosphates) through water exchanges, you will have less algae issues.

Sure, it’s hard work, but as I tell my clients, “That’s a concept I like to call, ‘job security.’”


The last issue I’m going to address is one of the more vexing issues for novice aquarium keepers, expert aquarists, and everything in-between: sick fish.

The fact is that sick fish are often difficult to treat, sometimes have poor prognosis, and the incidence of disease can have ripple effects on your aquarium stability.

Fortunately, we know of an intervention that will dramatically improve your odds of maintaining a disease-free aquarium, and it’s about the simplest concepts one can imagine: patience.

More important than the ability to diagnose fish disease is the willingness to patiently observe your new acquisitions in a quarantine system prior to introducing those animals to your display. In public aquariums all display animals go through a quarantine period, and even if those animals aren’t run through prophylactic-treatment regimen (most are), they undergo a prolonged “observational” period to make introductions of foreign organisms into displays as unlikely as possible.

Thus, even if you don’t treat your incoming fish specimens, simply keeping them in a smaller simple aquarium can prevent a calamity in your display aquarium. In addition, rather than disrupting the biological cycle of your aquarium (and risking a chemistry spike), it is not only prudent but also more economical to remove sick fishes from the main display and perform treatments in that quarantine setup.

These are just a few things you can do to help ensure that you have a successful and healthy aquarium.

Drop a comment below if you have ideas for future blog posts. No topics too big, no topics too small.


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