leaf loss on Ludwigia repens

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tomherndon

Aquarium Advice Activist
Joined
Oct 8, 2007
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North Carolina
Some of the stems and leaves of my L. repens are blackening and then 'wilting.' I'm not sure if it is exactly black, I'm a little color challenged, but not completely color blind. It's definitely darker. I've got leaves separating from the stems and suspending on the tank surface too.

The tank is a 10 gallon with 15 Watt general aquarium/plant fluorescent tube in standard reflector. The goal of the tank was to go low tech and balance the bioload. I have an 18 inch section of 3/4 in. diameter PVC half filled with gravel as an external filter and current generator. A small pump lifts water from the bottom left and the pipe returns to the top right. The substrate is terraced using tiles so water flows down across the gravel through the planted region in the tank bed to the pump. The water surface is rippled without the significant bubbling I've seen on my power and UG filters on other tanks. I'm hoping that I can remove the DIY filter at some point and just pump water directly from Lower left to upper right to create that current/surface disturbance.

The L. repens shares the tank with a few bundles of Valisneria spiralis, a small offshoot of java fern, six neons, a juvenile Cory and a multiplying herd of hitchiking pond snails.

After identifying the snail as the "garden variety" pond snail, all references (and my observations) do not identify them as a hazard to the plants, just algae grazers. They slide and glide all over leaves of both plants. Observations of particular leaves have shown no damage from the snail travel.

The tanks stays mid 70 temps and recent tests had nitrates around 10 ppm with a pH of 7 and a KH of just two.

I know this means the CO2 is a little low, but both plant species have been putting out new healthy leaves. Especially the V. spiralis. I've added 1/8 teaspoon of baking soda to each gallon of water during changes and topping off to promote the KH value a little. I don't think it's had a significant effect, but it made me feel like I was trying!

so I think I have three questions I need help on:

is this blackening followed by shedding of leaves a natural aspect of L. repens?

is the observation simply due to a low CO2 - should I need to fool with a yeast cell or step up the Khardening with bicarbonate?

is it possibly a plant parasite (and if so, what would I do about it)

any and all advice is welcome, I do not have photos of the tank at this time.

Oh, the tank lighting is timered to 4 hours in the morning and 5 hours in the evening.
 
My ludwigia repens has been doing the same thing in my 55 Gallon with 260 watts, dry ferts, and pressurized CO2.
 
I did lay in a fertile substrate under the gravel for the plant roots to tap. It's under several centimeters of gravel, but I figure the roots will have found it by now. The L. repens in on the second tier in my terrace. So (from the bottom up) it has 3mm soil, 8cm gravel, another layer of soil (obviously not uniformly distributed) with another 3-5 cm of gravel overtop. The plants were dug in almost to the higher layer of substrate and then pressed with gravel.

I haven't been adding any other fertilizers - hoping the fish and foodwaste would provide enought to satisfy the plant diet.
 
Here are my observations with Ludwigia repens:

I had this plant in a medium light, CO2-injected (pressurized) tank. It did wonderfully. I then placed some stems in a low light, DIY CO2 (yeast) tank. In this tank, the L. repens did what you are describing - some leaves turned black and fell off or I picked them off. I believe that this plant needs at least medium light for your size tank and it does better with pressurized CO2.

I do still have some stems in my low light tanks. I placed the stems where the light is the brightest. In my tank, that's front and center, not back in the corners, and as long as my DIY CO2 is putting out a steady stream of bubbles, the L. repens does moderately well. Not as well as with the higher light, CO2 pressurized tank, but it stays relatively nice-looking.

About your tank - how much is the water rippling? If the water is too turbulent, you are losing CO2. If I look up at my water surface, it is moving but not rippling or turbulent.

You may not really need to add baking soda to boost the KH. I don't do this in my low light tanks. I did add Alkaline Buffer from Seachem to my tank that had the pressurized CO2. I did this because I had a pH probe determining when the CO2 would come on, and without the extra KH (and pH) boost, the pH was too low to kick on the solenoid of my CO2 system.
 
thanks for all the advice, I'm going to look into stepping up the wattage.

I'm playing with the 10g's and hoping I can make most care mistakes before I take that big step to a bigger planted tank (55g?). Nothing beats experience for doing a good job of most things. . .
 
Experiment with the lighting - more will help. (make sure your CO2 level is adequate for your new lighting). What kind of fertilizers are you adding to the water column? A good substrate is fine for plants like crypts and swords but generally, stem plants are not heavy root feeders like the crypts and swords. Your nitrates look good. Try adding some potassium - Seachem sells some liquid potassium supplement. I use dry ferts but for a 10 gallon tank, the liquid fert will give you a pretty good value.

To answer your other question about plant parasites - You probably don't have any. This plant just needs more light and probably some water column fertilizing.
 
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