Another option may be to add the ferts dry all available from the board sponsors or other sources well documented in here. A lot of what and when to dose depends on your tank itself. I.E the amount of lighting is the biggest factor when deciding your dosing. Tanks are generally split into two categories low tech and high tech.
I always go to
http://www.theplantedtank.co.uk/ for a quick easy to understand reference on what to dose. Read up firstly on lighting and consider which category your tank will fit into. The two trains of thought are either dose more than you plants could use, the E.I method or match your plants uptake with the nutrients.
The advantage of E.I is that you know that all your nutrient needs are met so any problems are likely to be either co2 or circulation related. This is a slightly more expensive way of going about it but with the price of dry ferts is negligible and not really worth bothering about for the piece of mind.
The other way would be to dose at E.I levels and gradually reduce this down in 3/4 week blocks i.e dosing 10ml for 3 week then try 9ml for the next 3 weeks until at some point you notice a negative effect from the plants. This is itself is problematic as problems may manifest in algae which can arise quickly but take a long time to rectify even with good dosing. With a constant changing of biomass sometimes loads of plants and sometimes not due to a clip out it's a hard system to pin down. The choice is yours and tank specific.
As you can see in the link a tank your size dosing at E.I levels would need...
150-225 litres
1/2 tsp KNO3
1/8 tsp KH2PO4
1/8 tsp traces
Dosed at..
Sunday 50% water change. Add Macros (KNO3, KH2PO4)
Monday Add Traces
Tuesday Add Macros (KNO3, KH2PO4)
Wednesday Add Traces
Thursday Add Macros (KNO3, KH2PO4)
Friday Add Traces
Saturday Rest day
The water change is very important although I find 50% a bit excessive in my particular tank. Speeding up plant growth creates bi products from both fish and plants which in turn can cause algae issues. The other option would be to dose P.M.D.D style if your lighting is low enough, you have low light loving plants and the large water changes are not as important.
You can either just drop the dry powder into the tank or if you prefer mix it with water. The advantage of buying these powders is you get the raw ingredients. Buying commercially prepared ferts means you also pay for the bottle it's in, the water which is 99% of the contents of the bottle which is why a lot of people in here go down that route. I'm sure you have a bottle and some water at home
Whichever you choose is up to you as long as the right amounts are added per week.
Neil
