7 Reasons Aquarium Plants Rot and What to Do About It

Scientific studies have proven that there are health benefits to bringing the outdoors into our indoor living areas. Aquariums are a beautiful way to get that done with a combination of fish and plants, but what do you do when your plants become uncooperative and get sick – or even worse, begin to rot?

7 Reasons Aquarium Plants Rot: 

  1. They need more light.
  2. They need more CO2.
  3. Overgrown plants.
  4. Their bunching mechanism is killing their roots.
  5. The water temperature is too cold or too warm for that particular plant.
  6. Your fish are digging and uprooting your plants.
  7. Your fish are munching on your plants.

Live plants in your aquarium offer your fish some interesting areas for swimming and hiding. They also can give you a sense of calm as they gently dance in the water. We’re going to talk about the most common challenges you may face when planting in an aquarium and some things you can do to overcome those same challenges.

7 Reasons Your Aquarium Plants Rot

Let’s get our hands wet, dig into our aquarium, and learn how to keep our plants healthy.

  1. They need more light.

Like our indoor and outdoor plants, many plants that are grown in aquariums require a specific amount of light. Depending on the type of plant you’re caring for, its lighting needs may be anywhere from 10 to 40 lumens per liter of water.

It’s also important to consider that the light’s strength weakens as it gets farther from the source either because of depth or because of diagonal distance.

Tip: Adding reflectors to your tank’s lighting system can increase your light’s effectiveness by up to 4 times.

  • They need more CO2.

Your aquarium’s plants and fish need sufficient amounts of carbon dioxide to thrive. Conversely too much CO2 can be harmful to both.

To make sure you have the right amount of CO2 in your tank, you can purchase a CO2 system from your local pet store or from Amazon.com.

Tip: It’s best to turn your CO2 on at about Noon as your plants will soak up more of the water’s CO2 due to their exposure to natural sunlight.

  • Overgrown plants.

It’s inevitable…your plants are going to grow. As they grow, you’re going to need to consider some different options to make sure they can continue to flourish.

It’s important to make sure you are giving your aquarium plants plenty of room to thrive and continue to grow. If they have grown above your tank’s waterline, you will want to trim them back. If the leaves remain above the waterline, they will dry out, and your plant will become ill.

Tip: When you notice your plants are arguing for space inside their enclosure, consider trimming them back to give the base plants more breathing room. You might also consider dividing your plants and replanting one or two of them to a different location.

  • Their bunching mechanism is killing their roots.

When you bought your plants at the store, they came neatly bundled and secured together, most likely with a rubber band. They were grouped so nicely it made your plants look full and lush.

And they still can. It’s important, however, that you remove the rubber band that has held your plants together and secure them with nutrient-rich substrate and tank gravel.

Tip: When you are choosing which substrate is best for you, consider your fish’s ph needs as well.

  • The water temperature is too cold or too hot for your plants.

Think Goldilocks…not too hot, not too cold, just right. There are different types of plants that require different water temperatures. When you are choosing the plants for your fish tank, make sure you are comparing each plant’s needs with the others, so you have plants that are compatible with each other.

  • Your fish are digging and exposing your plants’ roots.

Similar to dogs, some fish just like to dig – it’s just in their nature. If these are the kind of fish you prefer, you’ll need to pay attention to the plants you have in your aquarium. You may choose to have plants secured to the bottom of your tank, or… you may choose to have floating plants that would not be disturbed by your diggers.

Tip: Some plants can be secured to a piece of driftwood or larger rock. This may be a viable option if you don’t want floating plants.

  • Your fish are munching on your plants.

Some fish are herbivores, and they go crazy when offered a buffet of plant life. If your tank is full of these fish, your plants are likely doomed. If you have just a few, your plants will be nibbled, but probably not destroyed.

Tip: Plant several different types of plants to give your nibblers plenty of options.

Which Live Plants Should I Put in My Aquarium?

Providing your fresh-water fish friends with live plants not only provides them with areas of interest, safety, and play, live plants also help keep the tank’s water clean and oxygenated.

If you are going to have live plants in your fresh-water fish aquarium, there are a few things you should consider:

Some species of plants are easier to maintain than others. Two such species are:

  • Water wisteria – This leafy plant’s leaf patterns provide tranquil movement in the tank’s water filter circulation.

The water wisteria also is a plant that will require very little care as long as it has 3-4 inches of gravel in which it can root itself. If your fish tank has a light on at all times, this will be the perfect plant as it prefers direct light.

  • Amazon sword – This leafy plant requires very little care, but it can grow to be quite large (up to 20” tall!), so keep that in mind before you choose it. Similar to the water wisteria, the amazon sword prefers direct light and will provide intriguing motion in your aquarium.

How large is your fish tank?

As we just discussed, the Amazon sword can be somewhat prolific. Several of the mosses will also spread across the area where they’ve been attached. You don’t want your aquarium’s plants overpowering your beautiful fish, so keep in mind the overall growth pattern associated with the plants you choose.

How much effort do you want to put into your fish tank’s plants?

Some plants, like the crypt wendtii can be somewhat temperamental and resistant to environmental changes.

If you prefer a no-fuss, no-muss approach to your aquarium, the crypt wendtii would not be a plant in which you would want to invest. Some love it; some hate it. If the plant isn’t happy with its environment, it has been known to “liquify” or disintegrate.

The pygmy chain sword, on the other hand, would be a plant that is reasonable for the novice and advanced hobbyists alike. It is not a temperamental plant and can be moved around the tank as desired.

TIP: There is charcoal that is specific to use in aquariums called filtering charcoal. Do not use horticultural charcoal in your aquarium as it can have adverse effects on your fish.

Do I Need to Prepare Plants Before I Place Them in My Aquarium?

Because plants can carry disease and/or undesired parasites or creatures, it is a good idea to quarantine your hydroponic plants for at about a week before you introduce them to your aquarium’s environment.

Here are some steps you can take to make sure your new plants will be safe for your existing plants:

  1. Dip your new plants in a bleach solution. To do this,
    1. Mix ¼ cup bleach with 3 1/3 cups of water in a container,
    1. Place your new plant in the bleach mixture for 2-3 minutes,
    1. Rinse your new plant with fresh water,
  • Dip your new plants in a saltwater solution. This is a similar process:
    • Mix ¼ cup of aquarium salt (kosher salt works too) with 4 cups of water,
    • Keeping the roots above the water line, dip your new plants for 15-20 seconds,
    • Rinse your new plant with freshwater,
    • Place your cleaned plants in dechlorinated water for one week then move them to your aquarium after their one-week quarantine period has ended.

Which Fish and Plants Don’t Play Well Together?

Silver Dollar Fish grow up to 6” long. Because of this, they can completely destroy your living plants with very little effort.

Scats are another breed to avoid. They prefer brackish water, which is not conducive to healthy plant growth.

Buenos Aires Tetras don’t get as large as the Silver Dollar Fish, but they seem to have healthy plant appetites. They also prefer to be part of a community of like fish, which makes the damage they create exponential.

I Thought Aquarium Plants Would Not Need Any Care

On the surface, it would seem so, but they are still living organisms that need specific care. Does this sound like a lot to have to do to care for your aquarium’s plants? Another viable option could be to have your fish swimming among faux plants and to create a separate indoor terrarium garden.

Terrarium Gardens What Comes First – The Container or the Plants?

Your indoor garden’s success is all about planning, planning, planning!

The first thing you’re going to want to ask yourself is: “What do I want to accomplish with this garden?” You may have different thoughts on this – feel free to think outside of the proverbial box.

  • Do you want to add some color to your living environment?
    • Do you want something that will fit on your end table?
    • Do you want something that will fit on the windowsill behind your sink?
    • Do you want something that will be a large conversation piece?
  • Do you want to grow your own herbs, so you have fresh spices for cooking?
  • Do you want to grow vegetables year-round?

Now that you’ve decided what you want to do, you can figure out what size of container you need.

Are there plants that are better for indoor gardening?

The direct answer is yes, but you can probably grow many more things indoors than you would think. This article by planetnatural.com provides a very comprehensive list, but here are some highlights:


  • Succulents – These are popular because they are fairly low maintenance and require little care.
  • Daffodils – Yes, you can even plant bulbs in your container garden and experience spring any time of year you want.
  • Bachelor Buttons – These miniature carnation-type flowers can provide wonderful pops of color year-round.

Note: Although planetnatural.com’s list includes Morning Glories, I would be cautious about this plant as it is actually a vine that is very prolific and spreads. This is not a plant you would want to transplant to your garden as its root system will take over your entire yard… and your neighbor’s yard.


  • Dill – Movies often show people growing their own dill (they must make a lot of potato salad). Did you know that there are many herbs you can grow indoors?
  • Lavender – In addition to being an interesting addition to some dishes, this herb has a proven calming effect and can be used as a sleep aid.
  • Chives – If you are one who doesn’t care for the strong or pungent taste of onions, chives can be a more subtle alternative.
  • Cilantro – Are you a salsa lover? What could be a better addition to your homemade salsa than fresh cilantro?


  • Cherry tomatoes – Having a side salad with dinner? Growing your own tomatoes indoors will let you have fresh tomatoes year-round.
  • Carrots – Yes, it says carrots. Clearly, any plant-like carrots or radishes that are root plants will need deeper soil, so they will require a larger terrarium.
  • Eggplant – Are you craving a vegetarian Italian dish? Eggplant parmesan can be on the menu. The other nice thing about Eggplant is the rich purple color provides a natural accent color to your décor.


  • Strawberries – Wouldn’t it be wonderful to have some of the small ever-bearing strawberry plants indoors that would allow you to have fresh strawberries in the middle of winter?

3 Reasons Your Indoor Plants Can Rot Too

Let’s get our hands dirty, dig into our aquarium soil, and learn how to keep our plants healthy.

  1. Overwatering and Not Enough Drainage.

Many plants that are grown in indoor containers do not typically need as much water as we are accustomed to giving our outdoor or deeply potted plants. Terrariums experience naturally increased moisture levels because of their mostly enclosed area.

Terrarium gardens don’t have the means to drain excess water as most potted plants can. This can result in the water pooling under the soil and creating a moldy environment. With that in mind, wait to water the plants in your aquarium until you can stick your finger deep into the soil level, and you feel mostly dry soil.

Tip: Provide a layered environment for your plants. This diagram is a great step-by-step for the best terrarium environment:

  • Too Much Condensation.

If your plant aquarium has a lid on it or has a smaller opening, you may notice condensation accumulating on the inside of your terrarium’s glass – particularly soon after you’ve watered your plants.

It may give an intriguing foggy, or frosted, look to your glass, but this accumulation of moisture on the inside of your planter may result in mold growth.

Tip: If you notice condensation collecting on the inside of your plant’s home, carefully wipe the glass dry. Should the condensation return, chances are you’re giving your plants too much water at once – decrease the amount of water you’re providing per watering session.

If your plants are in an enclosed aquarium and you notice condensation building, open the planter lid to allow excess moisture to escape.

  • Overgrown Plants.

It’s inevitable… your plants are going to grow. As they grow, you’re going to need to consider some different options to make sure they can continue to flourish.

It’s important to make sure you are giving your indoor plants plenty of room to thrive and continue to grow.

Tip: When you notice your plants are arguing for space inside their enclosure, consider trimming vines back to give the base plants more breathing room. You might also consider dividing your plants and replanting one or two of them to a different location.

Now that you know how to avoid providing a petri dish for mold to grow in your terrarium, it’s time to start growing plants!

Final Thoughts

No plant will live forever, but there are specific steps you can take to care for both your aquatic and container gardens:

  • Make sure that you have chosen an environment that is large enough to support your plant’s growth and your fish’s well-being.
  • Be honest with yourself about how often you want to care for your plants. If you don’t want to have to trim your aquarium’s plants regularly, focus on slow and low-growing plants.
  • Remember to put your plants in layers in your aquarium – taller plants in the back, shorter plants or moss only in the front.
  • Plants help keep your fish healthy. Similar to the role of plants outdoors, plants in your aquarium convert carbon dioxide into new oxygen and help purify the air
  • Get creative and let your imagination thrive while you are designing your aquarium’s new environment.