plants at the top turning yellow

[augi_ow]

my plants at the top especially the long growing ones are turning yellow to brown....
i don't know whether it's because when my water evaporates, the plants are like directly exposed to the light
the plants have minimal contact with water
the rest of the plants are growing very well (middle portion to lower portion)

my lightings are 72W PL.... 2 feet tank.. on for 10 hours a day

[PeterGwee]

[quote:7e0e58a07e="augi_ow"]my plants at the top especially the long growing ones are turning yellow to brown....
i don't know whether it's because when my water evaporates, the plants are like directly exposed to the light
the plants have minimal contact with water
the rest of the plants are growing very well (middle portion to lower portion)

my lightings are 72W PL.... 2 feet tank.. on for 10 hours a day[/quote:7e0e58a07e]

The intensity of light increases as the plants reaches for the surface of the water. What does this mark increase in light intensity drive? Yes..more uptake in nutrients and CO2. You'll be fine if you keep up on things and do not go the lean way of dosing nutrients (most folks still think lean dosing will avoid algae.) and keep up on the CO2 (can of worms... :P ..testing errors and measurements play a huge part here.).

The other possible issue is since the plants have less contact with water, they might start changing to emergent stuff?

Regards
Peter Gwee