I agree that your aquarium is probably closer to a small aquarium than a large one.
You may not need the Nitrates and Phosphates right now, but if your bioload stays the same while your plant mass increases it could reach the point where your Nitrates and Phosphates start bottoming out. If this occurs you would need to start dosing them. Maintaining at 10ppm really isn't that high.
My inclination would be to get all four ferts, since if stored properly they should keep pretty much indefinately. When I was getting started I bought each fert separately as I found I needed it. Wasted money on shipping and the plants continued to suffer while I was waiting for the later fertilizers to arrive. If I could go back I would just have gone ahead and gotten them all at once.
You may not need the Nitrates and Phosphates right now, but if your bioload stays the same while your plant mass increases it could reach the point where your Nitrates and Phosphates start bottoming out. If this occurs you would need to start dosing them. Maintaining at 10ppm really isn't that high.
My inclination would be to get all four ferts, since if stored properly they should keep pretty much indefinately. When I was getting started I bought each fert separately as I found I needed it. Wasted money on shipping and the plants continued to suffer while I was waiting for the later fertilizers to arrive. If I could go back I would just have gone ahead and gotten them all at once.