Before I respond to your question in post #14...Colin (post 15) had one suggestion for similar situations while essjay noted that 185 ppm (10 dGH) is not that hard for the fish under discussion. I concur with them. Now to peat.
Peat can be effective in some situations, but not in most. The issue is the GH and KH. Usually these are comparable, though as another member noted not always. But a high GH/KH will very effectively buffer the pH to prevent changes. If you were to add acid (via peat, leaves, or heaven forbid chemical concoctions, the acid would probably effect an immediate change but it would rapidly (usually within 24 hours, depending) bounce back. This is far worse on fish, and can kill them. The only way to safely and effectively (long-term) lower pH is to reduce the buffering capacity. That is what occurs inh my water I mentioned earlier in this thread. The basically zero GH and KH means the pH is "free" to do what it will naturally do. Adding organics like peat, wood, dried leaves will have some effect in my situation, which is how I get basically blackwater with a pH likely down around 3-4. Comparable to the Rio Negro in Amazonia, for example. But if I were to add organic matter to water with a significant GH/KH, the pH would not budge, at least up to the point at which the buffering capacity was reached, and then trouble.
The other thing about peat is that it rapidly "wears out." It would take a lot, depending, and it would need regular replacement.
