Who Gives A Fish Forums

I've had my tank up and running for a bit now, and I've noticed my duckweed is struggling. It's not just the duckweed, I've lost a few other plants too. The fish seem fine, but the plants just can't seem to make it.

To address the issue with your duckweed and other plants dying out, let's break it down. Plants require light, CO2, and nutrients to thrive. Given that duckweed is a surface plant, it's likely that light and CO2 aren't the culprits. This leaves us with nutrients as the probable cause.

Duckweed demands a substantial amount of nutrients, and with a large quantity of it in your tank, it's possible that it's depleting the available nutrients. To better understand the situation, could you share your water parameters with me? Plants need nitrogen, which duckweed obtains from nitrates in the aquarium. If your nitrate levels are extremely low, it's a clear indication that your duckweed is using up all the available nutrients, leaving insufficient amounts for your fish and any fertilizers you're using.

What type of fertilizer are you currently using? Most all-in-one liquid fertilizers contain negligible amounts of nitrogen. If your nitrate levels are very low, you may need to switch to a plant fertilizer rich in nitrogen. NA Thrive is a good option, but since it's an American product, you might need to look for alternatives in your region. In the UK, we have TNC Complete, and I believe Aquarium Coop and Tropica offer similar products.

You'll need to experiment with different fertilizer dosages to find the right balance for your tank. I would recommend starting with multiple doses per week and adjusting as needed. There's a concept called the "duckweed index" used in planted aquariums, where a small amount of duckweed is used as an indicator of nutrient deficiencies. Since light and CO2 aren't limiting factors for plant growth, any deficiencies in duckweed can be attributed to nutrient deficiencies. By dosing fertilizers to maintain healthy duckweed, you can be confident that your other plants will thrive as well.

That looks like frogbit to me, not duckweed - no problem in my opinion, duckweed can be a real pain and you already have surface plants. Frogbit doesn't like its leaves wet all the time, a bit of splashing or dunking is fine, but constant wetness causes them to go brown and die. With the Flex's tight lid, condensation builds up in the tank, so try raising the hood slightly and removing the cover from the feeding hatch if you have one.

There's a good amount of healthy new growth, so just remove the dead leaves and plants - you can do this weekly with water changes. Surface plants like frogbit don't need nitrates, they prefer ammonia, and your fish and fish food will provide that. If you do decide to fertilize, use a nitrate-free fertilizer like Seachem Comprehensive or TNC Lite. The recommended dose is fine, or you can try half the dose twice a week - that's what I do in my tanks, and they have zero nitrates without me adding any.

I'm pretty sure that's not duckweed or frogbit, it actually looks like Salvinia Minima to me.

Do you dose any fertiliser?

I had a similar experience with my Salvinia Seveflake a while back. It was thriving for ages, then suddenly it just started dying off. Initially, we thought it was due to a heatwave and condensation from the lid affecting the plants, but looking back, I think it was probably a lack of fertiliser that did it in.

I've found that with frogbit and duckweed, the length of their roots can be a good indicator of water quality. If the tank is running low on nutrients, they tend to stretch out. I've never managed to keep a tank clean enough to kill off duckweed, but frogbit seems more sensitive to changes in water quality. So, you might want to take a look at the roots rather than just focusing on the surface.

Duckweed can be a bit of a pain, but it's also a useful gauge of your tank's health. When it starts to struggle, it's a sign that your maintenance routine might need some tweaking.

I had Salvina and Duckweed in my tank early on. The Salvina eventually died off, and the Duckweed dwindled to almost nothing. But recently, the Duckweed has made a strong comeback. I'm not sure what triggered the rebound - maybe the increased water changes, the addition of a few more fish, or the root tabs for the other plants. My point is, as long as there's some Duckweed left, it'll likely bounce back when the balance in the tank improves.

Take a hard look at your tank's water and lighting setup. What kind of lighting are you using, and what's the spectrum like? How many hours a day is the light on?

Now, about the water parameters: what's the GH and temperature reading? pH is important too. Have you tested for ammonia, nitrite, and nitrate? Is your water from the city or a private well? If it's city water, what additives are in it? If it's a private well, has it been professionally tested?

What about fertilizers? Are you using any, and if so, what kind? Do you add salt to the water? Any other substances going into the tank?

That's Salvina minima. I've got duckweed down to a science - I actually grow it in bleach, it's super resilient. But Salvina minima? No idea, it's a mystery to me.