Very good post @FishFlow , the only fault in your logic being that Seachems flourish contains very little n-p-k, so your looking at having to buy a bottle of each of those also at approximately $8-10 a bottle.
This is why we're so hooked on NilocG or dry ferts in general.
When I ran the math initially it seemed to be about 10% of the cost of liquids (give or take). That assumes measuring your own dries . It's a LOT of math to truly compare the bottom line price which has to consider total nutrients in the tank.
Bottomline for me is I can dose my tanks an entire year for the cost of about two bottles of individual liquid ferts. Those bottles would be gone in a little over a month and I would still be missing some nutrients.
See Jocelyn's post above. It explains the amount of dosing required to achieve the same nutrient concentration using Seachem vs dry. It makes my head hurt a little. If I grew much tougher plants I would care more. E.I. dosing liquids will get scary expensive for much water.
Appears this thread has lost some steam.
As mentioned I use Option #2 - DIY EI Liquid Fertilizer with the provided bottles and pre-measured packets. During the discussions and other research, some members lower the dosages and they still see good growth. I decided to try it, as it happens I needed to create a new batch. Please remember this is in no way a scientific or controlled experiment.
So, I decided to do half of the pre-measured packets (Macro and Micros) and only dose excel every other day (yes, I have even forgotten to dose now and then). Also, root tabs and weekly 40-50% water changes.
Lets not forget, I have re-scaped the 55. To my surprise I see no negative results, the growth has been good and even surpassed my expectations. See pics of the re-scape start 2/10/18 and most recent. Just thought I would share.
I have read through this thread again to evaluate how I want to proceed with dosing fertilizer. I had just stocked up on flourish, trace, iron, and excel so I will deplete those before ordering dry fertilizer, but that is what I plan to do. I think I will go with the easier option #2 with the two bottles. I have 8 planted tanks and intend to have 9 once I rescape the 120g.
You dose fertilizer every day? With liquids, I am dosing flourish 1x a week, Trace 2x a week, and Iron when needed. Excel gets dosed 3 times a week when dosing ferts. Using dry would add to my daily routine since days will not be skipped.
Do you dose excel every day as well (if you do not have CO2 injector which is another topic I would like to learn about, but that's another thread)?
I am quite convinced it is a grand experiment to dial in our particular plant load, water chemistry etc. While it very easy to find charts with precise guidance, it doesn't take too long to figure out it is actually just a starting point. My half dosed tanks sure look a lot like my full dosed or overdosed tanks after 8 months..
Agree with @OnTheFly
Just an "Algae grower" here ( maybe a step above) LOL
As any newbie I struggled with what, how much and how often to dose the ferts. It literally had my head spinning. Happened upon some threads @OnTheFly and @toolman were participating in on another forum. Figured I would give it a try. It was so easy and less $'s, very good growth, following the dosing recommended. Then @OnTheFly mentioned he reduced his dosing. I thought Why? Even though we are using different methods. As mentioned above, decided to reduce the dosage and the prove is in the putting. Again each tank is as different as a fingerprint (Substrate,Light,Inhabitants and water parameters). So it is a grand experiment.