We are now at approx. the 3 week mark since placing the blocks inside the tanks. You'll recall that the manufacturer states that up to 4-6 weeks may be required, though some see results in just a few days. General thoughts as follows:
SE Asia: I have never seen the specimens in this tank so vibrant in coloration/health. The 5 gold gourami have all taken on black vertical banding with white ID at the fin tips. The 3 reticulated loaches have taken on a golden shine to their scaling; for a while I was concerned it was 'gold dust disease' until flashlight inspection revealed that the coloration was actually within their scaling bed; truly beautiful! The old-man, stunted ID shark (who grew up in poor conditions) is growing (!) and more incredibly, his front whiskers are growing back in. They are now ~1 inch long.... in 9 years he has never been seen with anything but short whiskers that lasted more than a week. This is simply unheard of. The 6 new green tiger barbs have been in the tank ~1 week and are similarly showing great color progression.
Lake Tang: The bichir has similarly shown a deepening of rostral coloration. After being a 'grey fish' for nearly a decade, he now seems to have some interesting coloration patterns. The juvenile comps continue to grow and have ~doubled in size from arrival. For such a slow growing species, I've been impressed with what I've seen. They are being very well fed and I'm trying to get them to take more veggie flake. They are supposed to be Gold Heads, but at the moment the dominant coloration pattern is vertical banding of muted brown with white fin speckling.
I do not know what has brought these changes on but the speculation can continue.... coincidence? Grass bacillus? Natural tank maturation?