Phosphate Levels & Lighting

[conorod]

I have an 80L tank with Limnophila Sessiliflora, Vallisneria sp. "Tiger" and dwarf sag. The vallisneria is doing well & sending out runners quickly, dwarf sag is OK but growing very slowly.
The limnophila was doing well for the first few weeks, and is still actively growing & sending out runners, but a lot of the older leaves seem to be struggling (curling, with some brown spots). The stem on the left in my photo is an example. I have noticed some brown leaves at the top too (although not sure if this is deficiency or algae) and a lot of broken leaves on the top of the water/in my filter/etc. I do have some amano shrimp that like to pick at the plant, but from what I've read they shouldn't really damage healthy leaves.
From what I've seen online this could be a phosphate deficiency, and when I tested it (JBL Test Kit) it didn't detect any phosphate in the tank. I have EasyLife Fosfo which I can add, but am wondering what phosphate level I should aim for in a planted tank?

I was also wondering about lighting - the tank is 80cm long * 30cm wide * 35cm high. Currently I'm using the light that came with the tank which is an 8W (900 lumens) LED. Is this enough for a planted 80L tank, without CO2? There is a second slot in the lid so I could get a second light bringing it to 1,800 lumens.

 

[StevenF]

There are 14 essential nutrients that plants need grow. The doesn't include CO2 and light. insufficient levels in any one of the 14 can cause what your are seeing. From my own experience you don't have a lighting or CO2 issue. IF the damaged is focused on lower leaves it indicates mobile nutrient is the problem. Mobile nutrient are nutrients plants can move from old tissue to support growth new tissue. That cuts the 14 nutrient downed to N,, K, Mg, P, Cl, Mo, Ni.

N (nitrogen) is the most heavily used essential nutrient in plants. What is your nitrate ammonia, nitrite readings if it is all zero you are deficient in nitrogen. Many nitrate fertilizers also are rich in K(Potassium). Also most phosphate fertilizers are also rich in K.

Mg (Magnesium)is probably the most common mobile nutrient deficiency. The GH test only detects calcium and magnesium. Plants both are essential and both are frequently causes of plant deficiency problems. You don't want a zero GH. tap water typically has some but depending on the source most of it might be calcium with little to no magnesium.

Mo (Molybdenum) and Ni (nickel) are only needed at one part per billion levels. It should be present in tap water and generally isn't a problem. but will not be in distilled or RO water. Are you using tap water?

Cl (chlorine) that gas is toxic to pants but chloride salts are safe. if your are using tap water (which was sterilized with chlorine gas) there should be some chloride salts in it. Always use a water conditioner with using tap water. Again RO and distilled water will not have any Cl.

You only listed one fertilizer which does have potassium and phosphate. But you listed nothing else. If you are not using a fertilizer you likely have multiple deficiencies but they are not sever enough to affect all plants. You might be better off using a complete fertilizer in stead of a just a KP fertilizer. In most cases a P of 1 part per million would be enough. Also always do a water change once a week. Not only does it keep the water clean but it adds Ca,Mg, Cl, Mo, and Ni.

 

[conorod]

Sorry I meant to state the fertiliser I use in my post - I use EasyLife Profito (which does not contain N/P/K), and EasyLife Kalium (for K). I had assumed that the fish & food would provide enough N and P but seems I may have been wrong.
I tested yesterday before my weekly water change and my readings were ammonia 0, nitrite 0, nitrate 20ppm. I do 50% water change per week, and use tap water.
Given I also seem to need to add P now, it probably does make sense to use a complete fertiliser. I was wary of doing so initially as I was worried about adding more nitrogen to the tank.

 

[Colin_T]

The Ambulia looks fine. The leaves are bigger at the top of the plant because there is more light near the surface for it. The smaller leaves at the base of the plant are just older and the plant didn't get as much light back then.

Phosphates do not normally occur in natural water ways and do not belong in aquariums. Terrestrial plants use phosphate to strengthen their cell walls and develop bigger root systems. Most aquatic plants get their nutrients through their leaves and have minimal root systems.

Phosphates are poisonous to fish and other aquatic organisms.

Terrestrial plant fertilisers are different to aquatic plant fertilisers.

 

[conorod]

Thanks for the replies! Appreciate the detail on what phosphate does for the plant, I can see why that wouldn't be as important for aquatic plants.

In terms of lighting, is 8W/900 lumens (for 10h/day) enough for this tank without CO2? That's just what the tank came with but I've heard that some of these plants (dwarf sag in particular) prefer higher light. I do have a second fitting in the lid so could add a second one bringing it to 1800lm.
I know ideally I would measure PAR but I don't have a meter for that and they seem expensive.

 

[Colin_T]

LIGHTING TIMES
Most aquarium plants like a bit of light and if you only have the light on for a couple of hours a day, they struggle. If the light doesn't have a high enough wattage they also struggle. Try having the tank lights on for 10-12 hours a day.

If you get lots of green algae then reduce the light by an hour a day and monitor the algae over the next 2 weeks.
If you don't get any green algae on the glass then increase the lighting period by an hour and monitor it.
If you get a small amount of algae then the lighting time is about right.

Some plants will close their leaves up when they have had sufficient light. Ambulia, Hygrophilas and a few others close their top set of leaves first, then the next set and so on down the stem. When you see this happening, wait an hour after the leaves have closed up against the stem and then turn lights off.

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TWO LIGHT UNITS
If you have two light units on the tank, put them on timers and have one come on first, then an hour later the second one can come on. It will be less stressful for the fish.

In the evening, turn the first light off and wait an hour, then have the second light go out.

If the lights have a low, medium and high intensity setting, have them on low in the morning, then increase it to medium after a couple of hours, and then high for the main part of the day. In the evening, reverse this and have the medium setting for a few hours, then low. Then turn the lights off.

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TURNING LIGHTS ON AND OFF
Stress from tank lights coming on when the room is dark can be an issue. Fish don't have eyelids and don't tolerate going from complete dark to bright light (or vice versa) instantly.

In the morning open the curtains or turn the room light on at least 30 minutes (or more) before turning the tank light on. This will reduce the stress on the fish and they won't go from a dark tank to a bright tank instantly.

At night turn the room light on and then turn the tank light off. Wait at least 30 minutes (or more) before turning the room light out. This allows the fish to settle down for the night instead of going from a brightly lit tank to complete darkness instantly.

Try to have the lights on at the same time each day.