Bad soil mix?

[Trip Dr]

Greetings all, hoping someone can give me some input on this one.  I've only really grown t. pachanoi and t. peruvians before and never had any issues with these.  I've pretty much just plonked bits into whatever soil and they grew.  Recently i decided to get a t. pachanoi cristate and a t. bridgesii monstrose to add some variety.  I did a little research online for a 'cactus mix' soil recipe.  What I came up with:

1 part premium potting mix

1 part perlite

1 part coir

1 part gravel

 

I also lined the bottom of the pot (~40mm) with pebbles in a bid to improve drainage.  I've since read this may not be a good idea.

 

Now this was a little bit modified from what i had read, but i figured it was close enough.  The issue I'm having is that my cristate and t. bridgesii are not looking as healthy as when i received them a few weeks back.  They have lost their deep green colour and are going a pale green.  See attached pictures.  I've also notices some 'scabs' forming on the side of my bridgesii.  

 

Now, I have a few ideas which might be causing the issue:

1. Too much sun - these guys were getting probably 2 hours in the middle of the day.  I'm in NW NSW, so bloody hot

2. The gravel was contaminated - I found this gravel on the side of the road.  I washed it till clean.  Maybe it had some oil on it, but i doubt it - i used a similar mix on a bougainvillea and it is thriving

3. Pebbles in the bottom - not holding enough water? 

4. Coir is in big chunks - I'm not 100% its coco coir as it didn't say coconut on the brick, but couldn't think of what else it might be.  The big chunks are about 25mm square.  I thought this could be holding too much moisture or perhaps is breaking down and releasing some compounds the cacti don't like.

5. I live in a town where all the tap water is bore water - it is generally hard, with an EC ~700us.  

 

Any thoughts or suggestions would be greatly appreciated.  Apologies if this is something that has been covered many times.

 

 

Edited April 3, 2018 by Trip Dr

[zelly]

Imagine for a moment you are a small tiny cactus plant with very minimal watering requirements.......

 

 

only you find yourself planted in a ginormously large pot completely surrounded by waterlogged soil with no chance of ever drying out.......

 

then compound the issue with absolutely horrible potting soil.........truly a recipe for disaster.

If you're in australia I'd highly recommend you give Dr Greenthumbs a shoutout

 

 

[Trip Dr]

Thanks for the reply Zelly.  It just goes to show I've been lucky so far.  I'll try get in touch with Dr Greenthumbs.

 

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