First check whether the brown is on the leaf or inside it. A removable surface film, an old leaf dissolving after planting, and a plant losing healthy new growth are different problems. Do not increase light or add several fertilizers before making that distinction.
Try one gentle wipe
Inspect an affected leaf and wipe a small area gently without damaging it. If the brown material lifts away and green tissue remains, investigate an algae or debris coating. If the tissue itself is translucent, soft, or breaking down, treat it as deteriorating leaf tissue.
Remove loose debris and review lighting and maintenance. Do not automatically add an algaecide, particularly in a tank with sensitive plants or invertebrates.
Was the plant recently submerged or moved?
Some aquarium plants are grown above water in humid conditions and replace those leaves after submersion. Cryptocorynes may also lose leaves after a change in conditions. New growth and a firm crown or rhizome are more useful observations than the appearance of one old leaf.
Aquarium Co-Op’s explanation of plant melt describes this transition. Remove fully deteriorated leaves, keep the growth point correctly planted, and avoid uprooting the plant repeatedly.
Check planting depth and physical damage
A buried Java fern or Anubias rhizome can deteriorate. A crushed stem or a deeply buried rosette crown can also prevent establishment.
Inspect how the plant is anchored before changing the fertilizer. Check for fish grazing, digging, or tearing leaves, especially when holes or missing sections appear.
Assess the light actually reaching the plant
Lower leaves can be shaded by dense stem growth or floaters even when the fixture is bright. Trim or thin the obstruction and keep a consistent timer. For an attached shade-tolerant plant, more intensity may create algae problems instead of helping.
Compare the requirements of the actual species with its position. The planted-aquarium guide helps coordinate the light with the rest of the setup.
Review nutrition without diagnosing by color alone
Check the fertilizer label, dose, and schedule, along with whether rooted plants have access to suitable root nutrition. Fish waste may supply some nutrients while leaving others short.
Holes, yellowing, or pale growth are clues, not proof of a single deficiency. Check the distribution of damage and the age of affected leaves. Do not add extra ammonia to an aquarium containing fish to “feed the plants.”
Measure improvement in new growth
A dead section will not turn green again. Make a reasoned adjustment, record it, and watch the next leaves. Persistent decline across several plants calls for checking water preparation, temperature, dosing errors, and recent chemical treatments rather than continuing to increase light.
