Why Your Aquarium Plants Turn Yellow, Then Brown and Die!

Why Your Aquarium Plants Turn Yellow, Then Brown and Die!

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Cultivating plants in a fish tank can be very rewarding, but you need to know how to take care of them in an aquarium environment. Like fish, the plants need pampering every once in a while.

Neglected plants will develop deficiencies which lead to a change in the color and shape of leaves, and will eventually start losing the foliage before they die completely.

In my experience, plants in tanks with insufficient nutrients will turn yellow, brown, white, clear, or black depending on the deficiency and the water conditions.

For instance, insufficient lighting and nitrogen deficiency will cause plants to turn yellow or brownish, especially on older leave, sometimes even turning red. Younger foliage will grow slowly and die prematurely.

Though yellow pigmentation could also be a result of potassium or iron deficiency. Even so, low iron manifest in a sequence that starts with a light green or whitish color on leaves, that turn black, and die if you fail to remedy the situation.

For a better understanding of why aquarium plants change color and nutrient deficiency, please read on!

What Deficiency is Causing Which Color Change in You Aquarium Plants

As I’ve mentioned above, all plants with an inadequate supply of nutrients will have the colors on leaves changing and will look weak and droopy. But each deficiency manifest differently, albeit most plants turning light-green, then yellow, and eventually brown regardless.

So, how do you pinpoint what nutrients your plants are lacking by merely looking at them?

See below!

**#1—**Aquarium Plants Turning Yellow

Any nutrient deficiency that affects the development of chlorophyll in plants leaves will cause the foliage to turn yellow, which includes a lack of sufficient light for the plants.

Little or no nitrogen, potassium, iron, and magnesium in your water column will also lead to leaves turning yellow, but they mostly get a light-green tinge first, instead of the normal rich green look that gives aquarium plants the lush appearance.

If a lack of potassium is the main cause of the yellowing on your plants, the tinge will tend to be more on the leaves edges and tips.

Older leaves will also turn more than the young, strong foliage if the issue is insufficient nitrogen. Budding leaves or those that just developed will also grow slowly and may die prematurely.

Low magnesium can be identified through pale or yellow leaves, with the veins remaining green, particularly on older foliage.

Overall, fertilization is the easiest way to remedy this issue, though in the case of not enough light, getting full spectrum or LED RGB aquarium lights is recommended.

**#2—**Aquarium Plants Turning White

Although low iron is a major player in the whitening on aquarium plant leaves, a magnesium or calcium deficiency could also be the cause. However, water from most sources have enough calcium, so it’s most likely would be a lesser cause than the other two.

If magnesium is deficient, the plants will turn pale or yellowish, but the veins will remain green, or whichever color is normal for your plants. As it is the norm, older leaves take the biggest hit and will most likely die and fall off even when the rest of the plant recovers.

Low Iron, also called iron chlorosis or lime chlorosis starts with the leaves turning pale green, then yellow mostly in between the dark-green veins, giving the foliage a spidery look.

Over time, the leaves will become whitish and start dying back, then spread to the whole plant. Your plants will remain stunted even if they do not die completely.

**#3—**Aquarium Plants Turning Brown

Brown color on algae plants is a little technical to explain compared to yellow, white or clear shade because the cause might be any of several unrelated causes.

First, if the colors on your plants look like a slimy film covering the leaves and stem, that is most likely brown algae (diatoms).

However, if the brown color is within the plant’s system, then that is a deficiency of sorts. It could either be that your aquarium plants are not getting the necessary light spectrum or there not enough nutrients to meet the plant’s needs.

I’ll talk about diatoms a little later, at the moment let’s focus on nutrient deficiencies that may cause your plants to turn brown.

Typically, the first suspect would be potassium deficiency, which may manifest in the form of brown leaves curling on the tips and may also include chlorosis (yellowish) between the leaf veins.

Please note that the brown color on leaves could sometimes be a darker shade which may appear black and as separate spots or dots as opposed to smudges.

Another nutrient that may cause browning of leaves is phosphorous, but there is a caveat because instead of low supply, it’s excess phosphates that will result in brown plants.

It also could be excess nitrates in your tank, sometimes coupled with too many phosphates.

That said, the best remedy to brown or black leaves on aquarium plants, whether appearing as spots or smudges, is to expel excess nitrates and phosphates by performing large water changes. You may also want to re-evaluate your stocking guidelines as excess fish produce more waste thus more nitrates.

Reduce the amounts you are feeding you fish to make sure there are no leftovers in the fish tank. Ideally, your fish should be able to finish what you offer them within five (5) minutes.

However, if the browning is as a result of nutrients deficiency, fertilizing you fish tanks would better solution.

Given this background, you will also realize at times that the line between excess and a lack of nutrients is quite thin, so keep checking your tanks parameters to establish which remedy will work when.

Brown (Black) Algae Turning Your Plants Brown!

As I mentioned, if you notice the brown (black) turn on your plants is not within the leaves structure but a slimy film on top of the leaves, that is algae and not a nutrient deficiency.

I know it might be a little confusing, especially if you’ve only experienced blue-green freshwater aquarium algae.

Well, brown alga is also quite common and might cause a real headache. Usually, the remedy would be to give your fish less food and keep up with your aquarium maintenance schedule.

Reducing nutrients like nitrates, phosphates, and especially silicate will also go along way in keeping diatoms out of your tank.

Silicate gets into your tank through the water source or when you use specific substrates like sand, which contain some amount of the salt.

Please see this post for more insight on how to deal will brown algae (diatoms) in your aquarium.

**#4—**Aquarium Plants Turning Transparent (Glassy)

Spirdly, transparent leaves on aquarium plants is another complaint I get quite often, though not as common as the other issues.

From my experience, the condition is caused by a deficiency of some sort, same as any leaf color changes.

Most times, aquarium plants seem to turn transparent when there is not enough calcium and magnesium in the tank. But I’ve also had an experience with glassy leaves due to low nitrogen in level in my water.

So, consider adding a regimen with increased nitrogen, calcium, and magnesium, but be careful not to overdose your tank, even though plants will rarely take in more than they need.

How To Revive Your Aquarium Plants

I’m sure once you’ve established what is making your plants change color and die, you’ll want to remedy the situation as soon as possible.

But how do you go about it?.

Of course, fertilizing your tank and regulating the amount and quality of light your plants get is a good place to start.

Try to find a regimen that works for the specific situation you are dealing with.

As you may already know, your plants require a number of nutrients though the amounts vary. Mostly, this depends on whether the nutrients are macro or micro-nutrients.

Plants consume macronutrients such as nitrogen, phosphorus, and potassium in large quantities, and micronutrients like iron, boron, and magnesium in trace amounts.

So, add these nutrients depending on how much of each element is required. You will also realize that some nutrients such as iron don’t last long in the water, meaning you may want to dose more often.

Whereas, elements like nitrogen are needed in larger amounts, so add them in larger amounts and sometimes more frequently.

It also possible to get regiments that supply a specific nutrient depending on what your plants require. For instance, flourish-Iron is ideal in a tank with insufficient iron.

In newly planted tanks where almost all necessary nutrients are needed, I recommend using a comprehensive supplement, which is easier and faster to apply and not targeted at a specific deficiency.

The amounts you need to use in your tank will most times be indicated in the regimen. But it’s also advisable to apply your own judgment as different aquarium plants consume nutrients differently. Plus big tanks with more plants would need more fertilization than small aquarium.

Have fun with your planted aquarium

Eddie Waithaka

Resident Content Creator and Marketer at AquariaWise who talks about aquariums and fish and aquascapes a lot.

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