Interesting experienceI wouldn't touch Eco Complete with a barge pole. I have used it before. It is so sharp and abrasive that finally removing it is almost impossible without damaging the glass. It's a very hard mineral and will scratch glass easily.
This is the first instance that anyone has ever recommended it to me. I honestly thought that it had reached the dustbin of history several years ago.
Anyone who has done survey work on lava fields will know what I mean - that stuff will shred through shoes, clothing, equipment and tyres in no time. It took the barbules off my corydoras (even with a sand cap): I got those fish out and luckily they made a full recovery. When I started the hobby - Eco Complete was the first product that really wound me up.
I’ve used Eco Complete in the past (nutrient rich base layer, topped with EC) - as I wanted a dark fairly uniformly coloured non-dusty substrate; it’s definitely less sharp than Seachem’s Flourite range, especially Flourite Red which I found to be a very natural looking substrate with its graded gravel size and range of colour (though local Flourite can arrive quite to extremely dusty re transport and storage)
I kept Corydoras on both substrates and never experienced any negative effects (over 2-3 years)
But, I’ve not bought or used EC or Flourite since the advent of Tropica Aquarium Soil 😉
(Note I did purchase some EC bags that turned out to have many glittery fines - Carib Sea instantly replaced these, including fast shipping over 5000 km )