Mollies Terrible Fish To Keep – Your Guide To Avoiding Common
Have you heard the rumors? Maybe you read it on a forum or a friend warned you away: “Don’t get mollies, they’re impossible!” You’ve probably seen the phrase mollies terrible fish to keep and wondered if there’s any truth to it.
I’m here to let you in on a little secret from years of fishkeeping: mollies aren’t terrible, they’re just misunderstood. The horror stories of them dying for no reason or constantly being sick almost always stem from a few simple, avoidable mistakes.
Promise me you’ll stick with me. In this complete guide, we’re going to pull back the curtain on why these vibrant, active fish have earned a tough reputation. We’ll show you exactly how to sidestep the common pitfalls and create a thriving aquarium you can be proud of.
We’ll break down the most common problems with mollies, provide a detailed care guide with pro tips, and even discuss sustainable practices. By the end, you’ll have the confidence to turn one of the hobby’s most misunderstood fish into the stunning centerpiece of your tank.
Why Do Mollies Get a Bad Rap? Unpacking Common Problems
Let’s get right to it. The idea that mollies are terrible fish to keep didn’t come from nowhere. New aquarists often run into the same set of issues, leading to frustration. But don’t worry—understanding the problem is the first step to solving it.
The “Sudden Death” Syndrome: The Hard Water Secret
This is the number one reason hobbyists give up on mollies. A fish looks perfectly healthy one day and is gone the next. The culprit is almost always incorrect water chemistry.
Mollies are livebearers that, in the wild, often live in hard, mineral-rich water, sometimes even in brackish estuaries. They have evolved to thrive in these conditions. Most of our tap water, especially in certain regions, is quite soft.
When you place a molly in soft, acidic water, its body has to work overtime to maintain its internal salt and mineral balance (a process called osmoregulation). This chronic stress weakens their immune system, making them susceptible to disease and leading to what looks like a “sudden” death. It wasn’t sudden; it was a slow decline.
Disease Magnets? The Truth About Molly Health
Mollies are often accused of being prone to diseases like Ich (white spot) and fungal infections. This is a direct consequence of the stress from poor water conditions mentioned above.
A stressed fish is a vulnerable fish. When a molly’s immune system is compromised by soft water, temperature swings, or poor water quality (high ammonia/nitrite), common pathogens that healthy fish could fight off can easily take hold. They aren’t inherently sicker than other fish; they are just less tolerant of the wrong environment.
The Endless Fry Problem: Managing Livebearer Populations
So, you got your water parameters right, and your mollies are thriving. Congratulations! Now you have a new problem: babies. Lots and lots of babies. Mollies are prolific livebearers, and a single female can store sperm for months, producing new batches of fry every 30-40 days.
While fascinating to watch, this can quickly lead to an overstocked tank. More fish mean more waste, a higher demand on your filter (bio-load), and a greater potential for water quality to crash. This is a classic beginner trap that makes people feel overwhelmed.
Aggression and Bullying: Not Always a Peaceful Community Fish
Though often sold as peaceful, mollies can have a feisty side. Males, in particular, can be relentless in their pursuit of females. If you have the wrong ratio (e.g., more males than females), the females will be constantly harassed and stressed.
This stress can lead to clamped fins, hiding, and a weakened immune system. In some cases, a dominant molly might even bully other, more timid tank mates, especially during feeding time.
The Ultimate Molly Care Guide: Turning “Terrible” into Terrific
Now that you know the common problems, let’s build the solution. This is your complete mollies terrible fish to keep care guide to ensure your fish don’t just survive, but truly flourish. Follow these steps, and you’ll wonder why anyone ever had trouble!
Tank Setup: Your Molly’s Perfect Home
Giving your mollies the right foundation is crucial. Don’t cut corners here!
- Tank Size: Forget those tiny starter kits. For a small group of mollies, a 20-gallon (75-liter) tank is the absolute minimum. A 29-gallon (110-liter) or larger is even better, as it provides more stable water conditions and room for fry to grow.
- Filtration: A good hang-on-back (HOB) or canister filter is essential. You want a filter rated for a slightly larger tank to handle the waste produced by these active eaters.
- Heating: Mollies are tropical fish. Keep the water temperature stable between 75-82°F (24-28°C) with a reliable aquarium heater.
The Most Important Parameter: Water Chemistry for Mollies
If you remember one thing from this article, let it be this. Getting the water chemistry right is the secret to healthy mollies.
You’ll need a good liquid test kit, specifically one that measures General Hardness (GH) and Carbonate Hardness (KH), in addition to pH, ammonia, nitrite, and nitrate.
- pH: Aim for a stable pH between 7.5 and 8.5.
- GH (General Hardness): This measures calcium and magnesium. It is critical for mollies. Aim for a GH of 15-30 dGH (degrees of General Hardness).
- KH (Carbonate Hardness): This helps keep your pH stable. Aim for a KH of 10-25 dKH.
Pro Tip: How to Increase Water Hardness
If your tap water is soft, don’t despair! Here are some easy, safe ways to raise your GH and KH:
- Crushed Coral or Aragonite: This is the easiest method. Add a media bag filled with crushed coral to your filter or mix it into your substrate. It will slowly dissolve, releasing minerals and buffering your water to the ideal parameters.
- Wonder Shells: These are compressed mineral blocks you can add to the tank that slowly dissolve, releasing beneficial minerals.
- Commercial Buffers: Products like Seachem Equilibrium (for GH) and Alkaline Buffer (for KH) can be used to precisely target your parameters during water changes.
Debunking the Salt Myth: Do Mollies Need a Brackish Tank?
You will often hear that you need to add aquarium salt to a molly tank. While mollies can live in brackish (slightly salty) water, it’s not necessary for the common varieties sold in most stores today.
These fish have been captive-bred for generations in freshwater. What they truly need is the mineral content of hard water, not necessarily the sodium chloride. Adding crushed coral is a much better long-term solution than constantly adding and measuring salt. Salt doesn’t evaporate, so it can build up to dangerous levels if not managed carefully during water changes.
Feeding Your Mollies for Vibrant Health
Mollies are omnivores with a big appetite for algae and plant matter. A diet of just flake food is not enough and can lead to digestive issues.
- High-Quality Flake/Pellet: Use a quality flake or pellet with spirulina or other vegetable ingredients as the staple.
- Vegetable Matter: This is non-negotiable! Supplement their diet several times a week with blanched zucchini, spinach, or shelled peas. They also love algae wafers.
- Frozen/Live Foods: Offer treats like brine shrimp or daphnia once or twice a week to provide protein and encourage natural foraging behavior.
Choosing Tank Mates Wisely: Creating a Harmonious Community
To prevent bullying and stress, choosing the right tank mates is key. You also need to maintain the correct male-to-female ratio for your mollies.
Always keep at least two to three females for every one male. This distributes the male’s attention and prevents any single female from being exhausted.
Good Tank Mates Include:
- Other hardy livebearers like Platies and Swordtails
- Sturdy Tetras (Serpae, Black Skirt)
- Corydoras Catfish
- Bristlenose Plecos
- Gouramis (avoiding overly aggressive ones)
Avoid slow-moving, long-finned fish like Bettas or fancy Guppies, as mollies might nip at their fins. Also, avoid fish that require soft, acidic water, like Cardinal Tetras or Rams, as their needs are incompatible.
Sustainable & Eco-Friendly Molly Keeping: Best Practices
Being a great fishkeeper also means being a responsible one. Adopting some eco-friendly mollies terrible fish to keep best practices shows true expertise and care for the hobby.
Responsible Breeding: What to Do with All Those Fry?
You will have fry. It’s inevitable. Instead of letting them overpopulate your tank and crash your water quality, have a plan.
- Local Fish Store (LFS): Many independent (non-chain) fish stores will take healthy, juvenile fish for store credit. Call ahead and build a relationship with them.
- Aquarium Clubs & Online Groups: Local hobbyist groups are a great place to trade or give away your extra fish to other enthusiasts who will give them a good home.
- A Predator in the Tank?: In a larger community tank, some of the fry will naturally be eaten by other fish. While it sounds harsh, this is a natural form of population control.
- A Separate Fry Tank: If you want to raise them, a separate 10-gallon tank is perfect for growing them out until they are large enough to rehome.
Sourcing Healthy Fish: Choosing a Reputable Source
Start with healthy stock to avoid bringing problems home. When you’re at the store, look for fish that are active, have their fins fully extended (not clamped to their body), and have plump bellies. Avoid any fish in tanks with dead or visibly sick inhabitants.
The Real Benefits of Keeping Mollies (When You Know the Secrets)
Once you move past the myths, you’ll discover the immense benefits of keeping mollies.
- Stunning Variety: From the classic Black Molly to the golden Sailfin to the Dalmatian, there is a molly for every aesthetic.
- Active Personalities: Mollies are always busy. They are constantly exploring, grazing on algae, and interacting with each other, making for a lively and entertaining tank.
- Fascinating to Breed: For those interested, watching the livebearing process and raising fry can be one of the most rewarding experiences in the aquarium hobby.
*Great Algae Eaters: They will happily graze on soft green algae all day, helping to keep your tank looking clean.
Frequently Asked Questions About Keeping Mollies
Why do my mollies keep dying?
The most common reason is water that is too soft and/or acidic. Mollies require hard, alkaline water with a high mineral content (GH and KH). Without it, their immune systems weaken, leading to stress, disease, and death. Test your GH and KH, and if they are low, add a source of minerals like crushed coral.
How many mollies should I keep together?
Start with a group of 3-4 in a 20-gallon tank or larger. The most important rule is to maintain a ratio of at least 2-3 females for every 1 male to prevent the females from being stressed and harassed.
Are mollies good for beginners?
They are excellent for beginners who are willing to learn. If you understand and provide for their one major requirement—hard water—they are incredibly hardy and rewarding. They are not, however, a fish you can just drop into any tap water and expect to thrive.
Do I have to add salt to my molly tank?
For the vast majority of common, captive-bred mollies, no. You do not need to add aquarium salt. Providing hard, alkaline freshwater with plenty of minerals (using crushed coral, for example) is the correct and more stable approach.
Your Journey with Mollies Starts Now
So, are mollies terrible fish to keep? Absolutely not. They are simply fish with a specific need that has been widely overlooked. They don’t ask for much, but their requirement for hard, alkaline water is non-negotiable.
By focusing on providing the right water chemistry from the start, you bypass nearly all the common problems that give these fish their undeserved reputation. You now have the mollies terrible fish to keep tips and the complete guide to succeed.
Armed with this knowledge, you can confidently build a beautiful, bustling aquarium filled with these amazing fish. Go forth and enjoy one of the most vibrant and rewarding species in the hobby!
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