Plant Deficiences And Diagnosis

Peter F

Junior Poster
Jul 9, 2009
I have noticed some of my plants are developing brown spots on their leaves. On closer examination they could be pin holes that grow bigger into brown rusty looking marks.
This is happening on the older leaves but is also noticeable on some of the new growth of Amazon Swords.
There is also green spot algae on some plant leaves. However, plant growth is still good.

I think it could be Potassium or Phosphate deficiency but don't know!

My tank is 180ltrs I am dosing daily with 5 mls of Tropica plant nutrition and I use
Tropica plant nutrition plus (with phosphates) once a week. I also inject CO2 and carry out 25% water changes weekly.

I am concerned about over dosing but do I need to increase it and if so to what?

Regards: Peter


Plant Guru Team
Lifetime Member
Sep 23, 2007
South Florida
Hi Peter,

A few questions back please to help understand your setup?

Tank lighting type, wattage, duration, distance from tank, etc..

Method of c02 injection. How do you determine you have 'enough' c02? Do your plants pearl at all?

Substrate? Filtration, etc.

Tom and others have shown than excess nutrients in a planted tank do not by themselves cause algae. Many algae and poor growth issues are c02 related.

C02 must be both stable and sufficient for plant bio-mass and the light levels. Higher light requires more c02 and other nutrients and it is easy to think you have enough c02 when you dont. The only way to accurately measure c02 in the water is with a $2000 meter.

You may want to investigate another method or two to diffuse your c02 based on your current method. There are many to choose from based on each configuration. If you have a sump, canisters, etc. Many methods discussed in threads on this site.

Diffusor disks (you may need 2), reactors, needle wheel pumps, venturis are all valid good methods based on your goals.

So, you may want to switch to powdered dry ferts and the EI dosing method. This requires a 50 water change to reset nutrient ratios and the idea is to provide NON limiting amounts of macros and micros. This is much cheaper than buying the products and is easy to mix with water and dump in the tank. You can adjust the recommended dosages based on your tank and setup. I double the EI amount regularly for my size tank with no issues.

It is fairly easy to rule out N and P and macro deficiencies by adding non limiting amounts of these........It takes a tremendously high dosage of N and P to harm shrimp or fish and plants, so no real worry there.

We also need to do the same for c02 as it is one of the main plant fertilizers and drives the need for other ferts.

You may want to up the c02 slowly and watch the fish for signs of stress. If any, reduce the bubble rate. Observe the tank for 2-3 days with each increase of c02. The plants should react within 1-2 weeks of increasing the c02 with better growth and reduced new algae.

Circulation of the water so that all areas of the tank and plants get flow to wash away detritus and waste products and to bring nutrients and c02 to the leaves..

You want to have a surface ripple for o2 enhancement when c02 is on and only have c02 when the lights are on. Turn your c02 on 90 minutes or so PRIOR to lights on so the tank has c02 for a bit before the lights come on.

A couple of 50% water changes 2 or 3 times per week for 2 weeks with some manual removal and trimming of any bad leaves and stems will also help.

Hope this helps.

Peter F

Junior Poster
Jul 9, 2009
Re: Plant Deficiences And Diagnosis


My tank is a standard Juwel Rio 180 litre tank with T5 highlight lighting. 2x45 w tubes.

The light unit is about two to three inches from water to surface.

The filter, Eheim 2324 pro 700 litres per hour. Substrate plain fine gravel with fetilizer capsules added to the plant roots.

C02 injection is on two hours before lights on and off one hour before lights off, 60 bubbles per min . Light duration 6 hours per day on a timer.

The tank is heavily planted but the only plants affected are Echinodorus. All other plants show no signs of leaf damage. (Aponogeton, Crytocoryne, Windelov, Vallis etc).

Regards: Peter