Losing leafs on stem plants at lower levels.

Hello I hope someone can help me. I'm loosing leafs on my Hygrophila guanensis, but only at the lower levels ( from substrate to first 6"). The leafs from 6" up are in great condition. Water parameters are Ammonia 0 Nitrites 0 Nitrates 15/20ppm. Water change is is 50% once a week. Co2 is 2 bps, which gives me a 1 point drop on ph from 8 to 7. Substrate is gravel 5" deep. I use root tabs every 6/8 weeks. I do dose an all in one fert 20ml , 20ml extra potassium, 5ml liquid iron.
My light is a Fluval aquasky which runs for 8hrs with a 30 minute ramp up & down cycle. The aquarium is 55 gallons, but it's dimensions are 36" long 15" width 24" tall. It is a moderately planted tank. So is it a lack of nutrients or lack of light reaching the lower levels of the tank? Every other plant in aquarium is doing well.

 

Typically, densely packed stemplants tend to give up their older leaves that catch less light, in favour of new leaves. Or, just as plausible, a lack of flow in the same area.

In both cases, I'd cut the plants, remove the bare bottom part, and plant the newer part in the substrate. This time with more space between them. And check if the leaves move a tiny bit, to confirm there is sufficient flow.

Do you see any red/purple-ish colours of the veins, underside the remaining leaves? In which case, I'd say lack of phosphates. But since most of your plants are doing fine, I would be very very hesitant to change dosing.

 

That's a tough one to remedy.

Typically, densely packed stemplants tend to give up their older leaves that catch less light, in favour of new leaves. Or, just as plausible, a lack of flow in the same area.

In which case, I'd cut the plants, remove the bare bottom part, and plant the newer part in the substrate. This time with more space between them. And check if the leaves move a tiny bit, to confirm there is sufficient flow.

Do you see any red/purple-ish colours of the veins, underside the remaining leaves. In which case, I'd say lack of phosphates. Since most of your plants are doing fine, I would be very very hesitant to change dosing.

No theirs no red or purple in the leafs which are left on the plants, As regards to flow theirs plenty as I've a fluval 407 cannister going and a wavemaker to help push the co2 around the aquarium. The all in one fertiliser is TNC complete which has phosphates added.

 

No theirs no red or purple in the leafs which are left on the plants, As regards to flow theirs plenty as I've a fluval 407 cannister going and a wavemaker to help push the co2 around the aquarium. The all in one fertiliser is TNC complete which has phosphates added.

Then it's time to use the scissors. Alternatively, you cut the top parts and plant those in front of the bare ones, and let both old and new grow. Perhaps remove a few bare ones to create more space, especially for the new ones.

 

The leaves high on the plants shade the lower leaves.

 

Needs more light. Also might need to trim upper stems so that more light reaches the base

 

Needs more light. Also might need to trim upper stems so that more light reaches the base

I've considered replacing my aquasky with a plant 3.0, or rising the substrate at the back of the aquarium. I know which is the cheaper option but also involves more work and upsetting the aquarium, any suggestions on what use on rising the substrate without buying more gravel??

 

If everything else is doing fine, I would leave the lights alone.

I've used flat stones in a very distant past to heighten substrate in the back. Works OK, but eventually the substrate might even out.

Using stones similar to terrace cultivation is more effective.

 

I've considered replacing my aquasky with a plant 3.0, or rising the substrate at the back of the aquarium. I know which is the cheaper option but also involves more work and upsetting the aquarium, any suggestions on what use on rising the substrate without buying more gravel??

You can also just add another light. Two modern LEDs is pretty good already

How high is the light above the tank? Rather than raising substrate, you can bring the light down closer to the water. 24" is pretty high, so for my 75g which is 24" I place the light as close to the water surface as possible.

Other factors are water tint and surface film/floating plants. Those reduce light penetration quite a bit as well. Improving the water clarity and moving some surface plants around can help a lot as well

 

You can also just add another light. Two modern LEDs is pretty good already

How high is the light above the tank? Rather than raising substrate, you can bring the light down closer to the water. 24" is pretty high, so for my 75g which is 24" I place the light as close to the water surface as possible.

Other factors are water tint and surface film/floating plants. Those reduce light penetration quite a bit as well. Improving the water clarity and moving some surface plants around can help a lot as well

The water clarity is good, the thing is my aquarium has glass sliding condensation plates which can be removed. I keep them clean as can be. As regards to the height of the light it can't get no closer as sits around 3/4" above the condensation plates. I won't consider leaving the plates out as my wooden hood would begin to catch any evaporation.