Wah, I wonder what is that wonderful stuff you got from RuslanJamil?
Migh want to try it too!.

Try to find more information about Dernnele product on the net, and all the best I can get is here. It seems that they name it E15 and V30 for a reason. E15 dose on the 15th and V30 dose on the 30th of each month. And they dose it not based on water volume of the tank but based on top up water volume after water change, instead. Now I know why this product expensive. High concentration. Only need to dose about 1-2 times monthly. But I do not like the idea of dosing that seldom, because the less frequent you dose, the more chances (forgetful) that you don't dose at all. I am sure it is great product. I like the A1, for daily dosing of trace elements. Only 4 drops per 100 liters.

About all the sales pitch from various manufacturer, all i can hear and read is this or that product is 'good' for your aquarium and your plants. But how good it really is, you have to use it and see it for yourself. Every tank is different. Try to ask people at LFS selling the product, don't have any clues mostly. Display tanks is the best bet, IMO.

Best Regards