Substrate

I recently got asked about the best planting substrate for beginners. This can be a complex topic... allow me to try and explain as best I can so you can make an informed choice...

"Substrate" as a word is very generic and refers to a lot of different types of materials and it is important to distinguish between them. Be warned also that different manufacturers use different terminology too!

1. True substrate - as in something that goes under something (e.g. tropica plant growth substrate). This is a nutrient rich base layer that should be capped with gravel or preferably sand. Sand is preferable because you don't need as much depth of the product to create an effective seal. You don't need a thick later of such products as they are nutrient rich. About a cm is just fine. The cap should be at least 2 to 3 cm of sand or 4 to 6 cm of gravel.  This capping process means that when the nutrient run out in the substrate they are not replenished. So it is important to use roots tabs in the longer term to add nutrition to the base layer. When putting in the base layer take care to not get any near the tank glass, you don't want to see it once the tank is set up... leave a gap around the edges of your tank and fill this with the sand or gravel so this is what you see. This method is particularly useful for plants which grow extensive root structures and therefore feed predominantly from their roots. Plants such as echinodorus for example. You can obviously only clean the surface of the cap, deep gravel vaccuming will simply remove the substrate. The down side here is that if you want to move a plant at a later date it can be difficult to do so. Removal of the plant breaks the cap and releases nutrients clouds the water with the substrate. You would need to ensure the are is recapped and perform a 90% water change or two.  Of course this can be avoided by careful planting initially taking account for eventual size of the plants etc. This is also a very inexpensive method  the small volume of substrate (tank width x length x 1cm volume only required) and cheap gravel or sand.

2.A planting substrate or "soil". This refers to a granular clay or volcanic based product normally consisting of dark coloured small pellets. It is normally all that is used in professional aquascapes. These products are designed for growing plants in aquariums and come with a specialist price tag. Two things to consider though... often an initial ammonia release from these products for first few weeks of their life (tropica aquarium soil does not do this). Unless you are planning co2 injection and/or a carpeted foreground you can use rocks to separate planted area at the rear of your tank and cosmetic sand or gravel area at the front, and so reducing the amount of soil required. (TIP: use something like filter floss to ensure a good seal behind the rock work so you dont get the substrates mixing over time) Better for long lasting aquascapes as designed so nutrients can enter the soil from waste in the aquarium and from water based fertilisation so use of root tabs etc in the longer term not required (look up CEC cation excahnge rate for the science around this). More flexible as plants can more easily be moved. Dark substrates also better for many fish.

I hope that helps, and feel free to chuck any questions my way!

No as the smaller heavier sand particles will fall through the larger lighter soil particles. Ultimately you will end up with the soil appearing on top of the sand over time... I have heard it done with a very very thick sand layer but don't know if it stood the test of time.

To be honest I don't see any reason to do this as the high CEC product is there to absorb nutrients from the water and fish waste and make it available to the plants. If you cap it it can't do this. The nutrient supply will quickly become exhausted. Far better to spend (probably less) money on the substrate instead if this idle the route your going down.

1. It shouldn't require root tabs as the high cec is there to absord nutrients from fish waste and in the water column and make it available to the plants but after a few years you may want to target a couple of the heavy root feeding plants with some root tabs to maintain healthy growth.
2. No, perhaps a little local release of debris (nothing to write home about) but no discoloration. Maybe do a quick water change after a heavy planting session if you are concerned.