New plants propagating but not growing

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Aquarium Advice Apprentice
Feb 2, 2022
Vermont, USA
Hi, I am very new to planted tanks and could use some help. I have a 20g high tank that was once all plastic that I am trying to convert to a low tech planted tank. I wanted to start simple with low-light plants that do not require CO2. Since the substrate is medium/large gravel, I am starting just with column feeders. The only light I had to start was what came with the tank (Marina 20g high LED tank). I can't find any specs about how much light it provides, but suffice it say it is very little, for plants at least.

Approx 4-5 months ago, I added the following:

From LFS:

Java moss, tethered to driftwood
Anubias nana

From Petsmart, TopFin tube plants:

Java fern
Windlove Java fern
Malaysian Red Java fern
El Nino fern
African Water fern
Bacopa caroliniana

Before adding to my main tank, I gave all a bleach dip and quarantined for ~4 weeks in my quarantine tank, without any light.

My java moss and Anubias nana were growing like gangbusters, but all the others not so much. So, I upgraded to a stronger light, Finnex Stringray 2, which at the base of the tank provides ~75 PAR. My poor Anubias starting turning yellow and wilting immediately, I moved it back to the quarantine tank to recover and appears to have gotten back on track there.

My Bacopa, as far as I can tell, hasn't done a thing. I tried it floating at first, then 3 weeks ago I planted it in the gravel with a root tab underneath.

All the other ferns, and this has been true since establishment, are propagating new plantlets like gangbusters but won't themselves grow. Once the new plantlets were big enough, I would detach and then glue to a rock, gravel, etc. These new plantlets are growing long roots but the stems and leaves aren't growing at all following detachment, as far as I can tell, or if so only at a glacial pace. So I've stopped at this point doing anything with them, and let them detach on their own and just float around the tank. All my plants also develop brown spots/patches, which do not at all look to be algae, and are too numerous to be new plantlets starting.

So I just switched back to the original tank light, thinking the Stingray might be too strong. I had spent the last 2 months tinkering with various amounts of light, by occluding the light with tape or parchment paper, with no discernible effect, giving each change at least a couple weeks I'd say.

I fertilize once a week with Flourish, right after my weekly PWE. I currently have the tank stocked with 6 neon tetras, 4 cory cats, and a honey gourami. Water parameters are always very stable, 0/0/5, pH 8, Temp 76F.

Any thoughts/suggestions would be welcomed.

Any chance of a picture of the tank with the light on and a picture of the plants with spots?

How long are the lights on for each day?

Do the light units have adjustable colours (red, green, blue, etc) and intensity?
Thanks Colin, sorry for my delayed reply, have been busy...
The current tank light is a plain white LED. The stronger light that I was using and eventually took off (Finnex Stringray II) has white, blue, and red spectrum lighting, although none are adjustable (other than a low blue light only "moonlight mode"). I have the tank on a timer so it gets 9 hours of light every day.

Various photos of the tank and the plants are attached.



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Java Fern, Java Moss, Bolbitis and Anubias are all slow growing plants that don't need lots of bright light. Too much light will encourage algae to grow on the leaves. All but the Java Moss have a rhizome that should be above the substrate.

The baby plants will be from the extra light. The plants often produce a heap of babies when the days get a big longer and the light more intense. In a few months they should settle down and stop producing babies and start growing. But while they have baby plants growing from the leaves, they won't be growing themselves.

Keep a steady lighting schedule and weekly fertiliser and they should be ok.


You need a picture on the back of the tank to help the fish feel more secure. You can buy aquarium backings from any pet shop or online. You can also use coloured card or a plastic bin liner. Just tape it to the outside on the back of the tank.

Some floating plants like Water Sprite (Ceratopteris thalictroides/ cornuta) would shade the plants a bit and reduce the algae, as well as making the neon tetras feel safer from aerial predation (not that there's any birds in the house but the neons don't know that).
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