Mortis said:
Got it, need to have atleast some nutrients in the substrate. I guess it depends more on the plants as well right ? Heavy root feeders and most carpet/foreground plants do well in a nutritious substrate.
Well, perhaps I was a bit unclear. You don't "need" a nutritious substrate or even a minimal level of nutrients if you are dosing EI. It's simply that having nutrients in the substrate is better than not having nutrients in the substrate. This is like 4 meals a day being better for weight gain than 3 meals a day, but you don't really "need" 4 meals a day, do you?
Some people are against dosing the water column, or prefer not to dose the water as richly as EI allows. If you are dosing on the lean side, or if you are inconsistent with your water column dosing then it's a good idea to have a nutritious substrate. The criticality depends on the environmental conditions that you set in the tank. If your lighting is very high and your CO2 is high, or if your water flow and distribution is marginal then there is a greater likelihood that nutrients in the substrate will be helpful.
In my opinion the concept of heavy root feeding is a myth. Crypts, Swords and other so called heavy root feeders gain just as much from water column dosing as other plants. In fact, a large sword will strip your tank water of it's nutrients in a hurry. Their leaves have massive surface areas which they use to great advantage. There are one or two very good reasons for having a large root structure besides root feeding, and I think people forget about that. A similar story is found with carpet plants. If a nutritious substrate is available they will take advantage, however they feed from their leaves just as any other aquatic.
Mortis said:
It is basicaly fine brown gravel, about 2-4 mm in size with Laterite material mixed in. I would say the ratio between the intert (might not be) gravel and laterite is about 60 : 40 or 70 : 30. It is mainly rich in iron and has some micronutrients as well as organic matter so it should be wel balanced.
Just wondering what thoughts are on laterite as a substrate, especially in this case where it is mixed evenly throughout the gravel and not used as a base layer. Will it cause a lot of algae ?
River sand will work fine, especially if it's rich in silt. If the river is fast flowing then much of the nutrients get wash away, but in slow flowing rivers the silt falls out of suspension and enriches the sediment. There are some lake sediments which massively outperform AS as a direct result of their accumulated organic silt.
Laterite used to be considered THE sediment material due it's supposed high iron content, however experience has shown that it's severely overrated. Iron is a trace element. There is a reason these are called "Trace" and "Micro"nutrients, that being that the plant doesn't really need much of them so all the hysteria about laterite and it's iron content is completely overblown. The fact that laterite is a clay product is actually much more relevant.

A fact overlooked by so many. Clay has one of the highest Cation Exchange Capacities (CEC) of all sediment materials. CEC allows the sediment material to attract and to hold positively charged nutrient ions which can then be passed on to the plant roots. This is much more valuable attribute than just having iron, because it means that the sediment particles continually can pull nutrients from the water and transport them to the root hairs. Sediments having high clay content therefore is all goodness from that perspective, but you'd do well to forget about all that hoopla about iron. Dose your trace element mix as normal and focus on delivering the macronutrients N, P and K to the plant leaves. That's where you'll make hay. :idea:
Neither laterite nor nutrients can cause algae, so rest assured.
😉
Cheers,