Join Date: Sep 2003
Location: Somerdale, New Jersey USA
New plants can go up to a month without added fertilization. The store sells them right from the grower who pushes growth by loading them with nutrients.
You have good light, a lightly planted tank, with new plants that probably don't need any ferts, and you are dosing them. So, you are feeding the algae.
You need to cut the dosing down or out for a while. Lots of light needs lots of plants in a new tank, to balance the light level. Lots of Stems, and some floaters such as Egeria, Salvinia. Water Sprite can be either a floater or planted in the substrate. Plant as heavily as you can afford.
But before you buy the plants, shut off the CO2, and do a 50% water change. Then cover the tank for 2 days with blankets or trash can liners blocking out all light. After 2 days uncover and do another water change.....don't feed the fish.......re-cover the tank for 2 more days.
Uncover and do another 50%er and plant heavily. Start the CO2 up and keep it up. You caused a lot of the problem by letting it run out, but the odds are it would have occurred anyway because of excess nutrients.
The black out will clear up the algae(green water), but it will return if you don't plant heavier and dose only what the plants can use.
Don't like the sound of fish gasping at the surface. Do you know the kH of your water? If you are adding CO2, you need to have a kH of at least 3.0 °H. This will buffer the water and protect the fish. If you don't have one I recommend a kH test kit.
HAVE DISCS - WILL TRAVEL