We know that you have a good experience in cultivating in coxim, could you talk a little about this substrate?

I've been using coxim since 5 years ago. I am doing it in a gradually way. For each container I open, I divide into two cuts, I put one in coxim and the other in tree fern fiber.
I should say that the results obtained are identical. Concerning the fertilizers, as far as I am concerned, I don't see any difference, I apply the same for both substrates. I apply a granulated mixture of bone dust, Ricinus communis' bran and ashes from wood , 3 times a years, in September, January and April, not applying during the winter. There is no other complement.
First, I sink the pot into the water, I put the mixture, than I superficially water in order to permit the fertilizer works into the substrate and doesn't go away during this first watering. Nowadays, 20% of my plants are cultivated in cubes coxim.

What are the advantages of this substrate?

The aeration of the roots. The cubes can not be put in organized way, they should be throw freely, not compressed, allowing the suitable ventilation of the radicular system. I am just talking the coxim cubes, as a matter of fact, this aeration doesn't happen with the granulated so I don't think it works in this kind of presentation.
I can see another advantage. When we have to do the reppoting, when the decomposition starts, it is very easy to clean the roots. It can be completely eliminated with the water. They become clean and we cant put the new cubes among the roots, in the empty spaces, it is extremely simple. I've just done it with a Vanda in a wood basket.
It is a long lasting substrate and can be used for 5 years, it doesn't rot practically. It takes years to decompose and maintains the pH level at 5,4 until the end and in this way, it is better than tree fern fibers.

And the big disadvantages?

The disadvantages can be perfectly overcome.
First of all, the coxim must be soaked for, at least, 8 days, changing the water daily to eliminate the tannin which exists in the coconut bark. The tannin is highly harmful to the roots but after washing the coxim will be clean completely and adequate to orchids cultivation, humid without acidity.
On the other hand, although the tree fern fiber doesn't need to be soaked for long time, I have the same precaution. First of all, I sieve it to take off the powder and then I wash carefully to eliminate it totally. The disadvantage of the tree fern fiber is exactly this, the dust retains too much humidity and makes the roots decay. Coxim doesn't has this disadvantage.
Concerning the use, we must learn how to deal with it, the away of putting the plant in the pot is different. The tree fern fiber, for example, hold better the plant which stays more sustained. With coxim, we must hold it better in order to fix well the plant. It is a little more hard. I use the side small holes to tie it. I put the plant back close to the pot wall, pass a line through the closest hole, pass it around the plant, then through the same hole and tie it around the pot. I do the same thing with one of the other hole and if it is a hang pot, the wire also helps holding it.
I know there are some other methods but, in my opinion, this one is good. As I said, the disadvantages are perfectly overcome and don't discourage the use of coxim.

And about the humidity retention, is it good?

It is good provides you maintain the regularity of the watering in order to keep it always humid. The coxim claims for a little bit different watering, it needs care. The tree fern fiber, for example, need to be completely dried out before watering again but the coxim needs to be always humid, the surface dries out very quickly. This is why, I don't think it is a good substrate for orchids with delicate roots like Miltonia, Oncidium and so on... In this case, I prefer to use tree barks like cork, for example.

What do you think about the nutrition, has it the efficacy required?

As far as I am concerned, coxim is so efficient as tree fern fiber, both require an adequate feeding. As I've already said, I apply the same fertilizer system for both substrates and I get the same results.

You said that the aeration of the radicular system is not the same with granulated coxim. What do you think about the slabs?

I just use the cubes. The granulated becomes too much compact retaining too much humidity. While the granulated is harmful because the ventilation is not good , in slabs, it is quite the contrary, they dry out very quickly but also damaging the roots. It is very complicated to keep them humid. To me, coxim means cubes.

What do you think about all options we have?

The cork bark, as I said, is very good for Oncidium. There are some other completely neutral, for example, pebbles, piassaba and requires much more fertilizer.
Pebble retains nothing of humidity, piassaba retains a little, both are insufficient , the humidity must be uniform.
Piassaba has an interesting characteristic, it wears up but it doesn't decompose, it is used in the Northeast of Brazil to do chains cables for the boats. Pine bark makes me worried because here, it not disinfected and can bring diseases. It is used in United States but there it is sterilized.

Do you consider coxim the ideal substitute to tree fern fiber?

I consider coxim is perfectly adequate and I have been obtained good results with it. Except for the orchids with delicate roots, in my opinion it is, until now, the ideal substitute for tree fern fiber. If I must change all the substrate in my nurseries, I will change for coxim but I as long as I have tree fern fiber, I keep in using it and doing as I am doing until now, the most part of the plants in it, another part in coxim.

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