Planted Tank Guru
Join Date: Jun 2004
Location: Baton Rouge, LA
There are a lot of things going on here:
1) First, you have an awfully long photoperiod. Plants need "sleep" just like we do, and perform different tasks during the times of light and darkness. Though it's a matter of opinion, I'd say 12 hours max is acceptable, 10 hours preferable. Your health will gradually decline if you consistently get too little sleep, and so will your plants; even if they seem to be doing well at first.
2) Then, it sounds like you shortened leaves on your swords by cutting them. While I'm not sure about your swords in particular, not all plants tolerate this well. Leaves injured by cutting can slowly die off over weeks or months, and unhealthy leaves attract algae like a magnet. This may have been a major contributing factor to the algae's first appearance, though it may not have been the only factor. It's usually better to remove whole leaves. New ones will soon appear to replace what you remove.
3) Next, you used UV. This is really only effective against fine algae suspended in the water, like green water. It can't touch the hair algae already securely attached to plants, though it may kill the occasional fragment that breaks off before it has a chance to reattach elsewhere. UV also breaks down iron in the water, changing it into a form that precipitates out to the bottom of the tank, and that plants can't directly use. As it sounds like you're dosing all nutrients by adding them to the water, unless you compensated for this by dosing additional iron, you may have starved your plants of this essential nutrient.
4) Finally, you used "green a way". If by this you are referring to Interpet's Green Away, it too is only effective against green water; causing the fine suspended algae to clump together so it can be filtered out. Totally useless for your algae. While it sounds as if it would normally be safe, any chemical treatment has potential for harm, especially if plants or other tank inhabitants are already weakened.
A lot of small errors and unintended side effects, all compounded together into one big problem.
I think others are already covering possibilities of nutrient deficiency quite well, so I'll leave that to them; other than the UV/iron interaction I already commented on.