Temple plant (probably some sort of hygro) faling

The temple plant is losing as much as a leaf per day--- the leaves aren't discoloring or developing holes, just dropping off. I don't know why, but every morning I seem to find another detached leaf floating at the top of the tank.

The tank is a 20 gallon high which I just rescaped with new substrate--- I thought I'd try rooted plants for the first time, but I'm a terrible gardener. The substrate is Eco-complete (the black volcanic gravel one); I have a Fluval light which I'm running 7.5 hours per day and an Aquaclear HOB filter. I tried to root the new plants in the substrate by burying the bottom ends of the stalks. I'm not currently using any fertilizers, and I don't plan to use CO2 because I suspect I'd screw it up and kill everything.

My last ammonia and nitrites readings were low to undetectable; my last nitrates readings were 40ppm and 20ppm, which seemed high to me; the Ph is about 7.5.

The other plants in the tank are some java moss, some small java ferns (survivors of a great dieback in the old scape), some crypts (new, seem to be ok so far), and some other plants whose species I don't actually know (I suspect one of them is susswassertang but it's a volunteer; the other is a stalked plant with small round leaves which I bought at the LFS and forget the species of). The animals are a large population of red cherry shrimp, a large population of pond snails and two forktail rainbowfish (the rest of the school died off during lockdown and since I was planning to move house and rescape, I haven't gotten any more fish yet). I also have a pothos vine with its roots sitting in the water to try to lower the nitrates.

Any advice would be extremely welcome.

 

If the plants are new, they may drop leaves or melt while adjusting to your water, especially if they were grown emersed (out of the water) before you found them. Many aquatic plants can be grown emersed and it's faster and cheaper to do so, so many aquatic plant farms choose to do that. Ferts may not be necessary since you have live stock in the tank, but it largely depends on the types of plants, water source, and livestock/feeding. If it's a heavy root feeder, then root tabs may help. A pic of the plant would help people identify it so they could give you more info specific to that plant.

 

Yes, the plant may have been grown emersed: It may also have a phosphate deficiency or both. Plant Deficiency Picture Diagram

 

Thanks for your help so far. Here's the picture.

 

Yellowing of the leaves - Iron Deficiency. Here is some fertilizer to consider: https://www.amazon.com/Liquid-NPK-A...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

That doesn’t look like hygrophila much. It actually looks like a terrestrial plant, so that explains it doing so poorly in and aquatic environment. If it’s dropping leaves every day now it’s been seriously overwatered and is probably a lost cause. You could still pull it out and let it sit bare root for a day or so and see…