Dosing Tank With Fertilisers

[Kaidonni]

I'm trying to figure out if I should be dosing my tank with additional fertilisers. It's a 50L tank, Fluval 2Plus Internal Filter, 5 White Cloud Mountain Minnows, temperature 21-23.5C (I don't use my heater, but unavoidably the tank light does heat the water...it might even go to 24C), and the tank light is a Sun-glo 15W T8. Tank light is on 7 hours a day, 2pm-9pm.
 
Plants are a mixture of java fern, amazon sword plants (Byron suggested Echinodorus grisebachii), another sword plant I don't know the names of, elodea and some grass-like plants (I have no idea of the name again).
 
I dose with Seachem Flourish Comprehensive once a week, ~1ml the day after my weekly water change, more than 24 hours after the Prime has gone into the tank with the replacement water as it might 'detoxify' the fertiliser (and defeat the point of me using fertiliser). I am noticing that, in particular, the java fern don't do too well, with chlorosis developing on the leaves as well as leaves going light green/white.I do have to bury the rhizome partly into the gravel or the plant will just be sitting on top, and will get disturbed during a water change - maybe I'll phase them out as this is probably no good.
 
Do I need to dose with further Seachem Flourish Comprehensive, or would other fertiliser in addition to what I already dose be necessary? What to look out for and how much to dose to begin with?
Thanks.

 

[Byron]

I'll post to get this discussion started, since I just mentioned some of this in the other thread.
 
Plants grow by photosynthesizing, and they will do this full out provided the light is of sufficient intensity and the required 17 nutrients are available (meaning, in sufficient levels).  This balance of light (intensity plus duration) and nutrients varies with different plant species, and obviously with quantity (plant load).  All of these nutrients can occur from fish foods and water changes; the plant species and numbers determine whether this will or will not be adequate.
 
Slow-growing plants (Java Fern, Java Moss, Anubias as examples) tend to require less light and fewer nutrients.  Fast-growing plants (stem plants and floating plants in particular) require more light (intensity) and nutrients.  Too much light, too little light, too many nutrients, or too few nutrients...any of these can upset the balance and cause algae issues plus plant deterioration.
 
To the Java Fern.  The rhizome should be above the substrate or it will likely rot.  Attach it to bits of wood or rock.  Beyond this, it should be receiving sufficient light and nutrients now, but I would point out that you have made changes fairly recently [as we have been discussing in the other thread] and it takes a few weeks before you see results.  Also, existing leaves will not show these, only new growth or any non-affected leaves, so use these to gage results.  Also, this plant does seem to do better in a bit of shade, so I would consider floating plants.  This is more for the future, as left under direct light this plant is susceptible to brush algae, and your addition of fertilizers will encourage this should the nutrients exceed the needs of all the plants.
 
The grass-like plant I believe is Vallisneria, if I'm remembering the photos in the other thread.  This is a fairly fast-growing plant, as is the sword plant, so I would give things a couple more weeks to see if a second dose of Flourich Comprehensive is needed or not.  You have again just recently made changes to the lighting duration and fertilizer, so it needs time to stabilize.
 
Byron.