The Substrate.

I started with planted tank in the dark aquarium age --- the mid 1960s.

Washed sand was the normal substrate then. As my other hobby being gardening - I started experimenting with soils in my aquarium and the sun. Over the years I settled down with the present substrate that I use.

My initial experiments used soil I had prepared for my nursery seed-beds. These soil were rich but were short-lived as it got quickly gave off all their nutrient either to the plant or to the water column (when the latter happened I had algae blooms). I started to use more and more varieties of soil in the aquarium - looking for soil low in organic content and high in insoluble minerals.

Finally I found that the soil best suited for my planted aquarium was a very red clay that I obtained by screening the gravel at the laterite nodules quarry. This was virgin clay, no plants ever had its roots in this soil. Then this clay had a very bad habit of getting into the water and discolouring it yellow.

I tried many tricks to stop the water getting discoloured. Only 2 method were successful:-
1) I found if you wet the clay and mould it into small granules and bake it as you would fire pottery, the result would provide you with a long duration substrate which did not discolour the water. Took too long and much work.
2) So I tried to hide the soil under sand. I found that if I first laid the soil and then covered it with mosquito net and covered it with an inch of sand or gravel mix - the clay stayed put and did not discolour the water.

It is this second method that I favour these days. The only evolution to my red lateritic clay is addition of 1Kgs. of Single Super Phosphate, an agricultural fertiliser, for every CFt. of clay. SSP is one part calcium phosphate and 3 parts calcium sulphate. I added this fertiliser because the clay was, on analysis, was found to have very poor content of Ca, P, S.

I normally use 2" of this clay mix under 1" of sand/gravel in my planted tanks.