I would dose your nitrates up to 10 - 15 ppm. Then watch them over the next few weeks and see what you need to do. You can use this as a guide:
http://www.plantedtank.net/forums/sh...ad.php?t=21944
but each tank is different. As your plant mass grows, your nutrients will be depleted faster. Then if you do a big trim, they nutrient use will go down. Over time you get the feel for what it needs.
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29 gallon, Fluval 306. Aquatop PF25-UV Power Filter, 1x39 watt T5HO 7" above tank. P.F. Sand, Pressurized CO2, 5 Glowlight Tetra's, 3 Halequin Rasborah's, 3 neons, 2 Oto's, 5 Cherry Shrimp, 4 Amano Shrimp.