How To Know When To Trim Plants In Your Fish Tank (And How To Do It)

A lot of people have plants in their fish tank whether it’s for oxygenate the tank, provide hiding places or if you like the look of a planted fish tank. But if not maintained the plants can get out of hand and out-grow the tank.

When do you trim fish tank plants? You trim the roots right before you plant a new plant in a fish tank. You also trim the plant in the water when it’s not as visually appealing to look at. How often depends on the type of plant.

I will go thru with you, why you cut plants and how to cut the plants in your fish tank in this article.

Why cut the plants?

Why do you need to cut the plants in the first place? If you are not cutting the plants in your fish tank they will keep growing. That is if the tank is healthy. An un-healthy tank makes the plants die and in worst case rotting and that makes the water quality bad for your fish and they might die. It’s also a risk of algae growing when having an un-healthy tank.

If your fish tank is healthy and the plants are growing you need to cut them before they grow too large and blocking the light for your other plants. The light is vital for a plant whether it’s in the water or on the land.

Most of the time the plants that should be in the back of the tank, which is longer, is often growing faster than the plants more in the front of the fish tank. That makes the longer and bigger plants blocking the light for the plants in the front and make them grow slower or even die. That’s ruining the look of your planted fish tank.

That’s why you need to keep an eye on the size of your plants and trim them if they are getting too big.

The plants in the mid-ground and foreground should also be trimmed. It’s not because they are blocking the light since they are often lower in height. They should be trimmed because they will ruin the look of your fish tank if they grow too wild.

Maybe you want the “wild” look in your tank but most tank looks the best when they are well maintained and trimmed. If you want the look, trim it, but trim it into that look.

Another reason to trim your fish tank plants is to trim off dead leaves. The plants’ leaves are dying, there is no escape of that, and when they die they will not release the leave all the time.

You should not let that leave on the plant since as long as the leave is attached to the stem it will drain nutrients. That makes fewer nutrients to the healthy leaves and making them grow slower and more likely to get a shortage of nutrients. A shortage of nutrients makes the plant look ugly and unhealthy and will not grow into that beautiful plant you have visioned in your head when planting the fish tank.

When buying plants you should trim the roots if they are too long. 3 cm or an inch is a good length before planting. That makes the plant grow new roots and will get anchored in the substrate quickly after planting.

Check the plants regularly to see if they need trimming. A good time to trim the plants is when you do a water change since there might be particles and leaves from the cut plants floating around that you will get rid of during a water change.

Cut for regrowth

It’s not only beneficial to cut the plant to shorten it. It also benefits the growth of the plant making the fish tank be denser planted.

When cut the plant will grow more stems making it grow denser. If you are having fast-growing plants, the plants will quickly grow to a thick “hedge” making the fish tank more green and beautiful. It also makes the fish and shrimps like you more because they will get good hiding places.

When cutting you will get a new healthy plant, if you cut off a healthy plant and not a dead leaf. All of a sudden you have two plants, the one already planted and one in your hand. The part you cut off you should replant.

When replanting you should put it close to the other plants making the plants denser-looking. If you don’t want to plant and are satisfied with the number of plants in the fish tank you don’t have to plant the cutting.

Instead, you could sell or give away the cutting to somebody else.

How to trim a fish tank plant

So, how do you trim the plants?

First of all, you need some tools. You really only need a scissor to be able to trim the plants but I would recommend getting the right kind of tool. The right kind of tool is longer tweezers and scissors. The scissors are sharp and will make a good cut on your plants, not damaging them. The tweezers help you to put the plant in the substrate without disturbing or damaging the roots.

Amazon has good tools for a good price. You should buy them in a kit to get them cheaper. The curved scissors make it easier to get into places where it might be tight and it also makes it easier to trim the plants growing near the bottom of the fish tank.

How you cut your plants depends on which type of plant you are cutting.

Stem plant

Stem plants are plants growing on stems. These are fast-growing and will grow two new stems from the cut part of the plant.

You should cut these plants from the top and not from the root. It won’t damage the plant but instead making it grow more. What could damage the plant though is if you cut it more than half of the plants’ length.

These plants could be replanted when cutting off.

Potted plant

Potted plants grow slow. They don’t grow upwards, they grow more sideways making them grow denser. When trimming this kind of plant you cut them near the root, not from the top like you do with stem plants.

If you cut them across the leaves it could damage the plant. Also, it doesn’t look good in this kind of plant.

It could be a challenge to maintain this kind of plant since it grows dense and you should not cut it in length. Therefore it would be recommended to get the kind of potted plant that grows in the length that you want.

Moss is easily maintained since they grow slow in good water conditions. You cut them at the top and into the length you want. The cuttings could be retied to a stone or furniture.

When cutting moss it’s a good idea to have an angeled scissor to have better control of your cutting.

Java fern and Anubias are plants having a rhizome. The rhizome is at the bottom of the plant and to trim it you simply cut the rhizome and replant the part you are taking off. It’s recommended to not cur more than 2-3 parts of the rhizome to not risk damaging the plant.

You could trim the plant from the top if it grows too tall. be careful not to cut too much of the plant since it might damage the plant.


I have been a fish keeper a big part of my life. During the years I have gathered and searched a lot of information about fish keeping and here, on the website, is where I share that information to help you with your fish keeping. I want to provide the information that I didn't get when I had a question about my fish tank.

Recent Posts