mikev wrote:An excellent summary, Emma, this should be kept somewhere permanently.
Thank you!
mikev wrote:One question that makes me curious: hardness. Is there any evidence/example that soft water may be wrong for a hard water species?
The reverse is obviously true, for loaches and perhaps even more for plecos, but is there any fish that actually needs/may use dissolved solids?
Although not completely answering your question, the following information, taken from the Interpet Manual of Fish Health, and written by the knowledgeable Adrian Exell, may be of interest:
"
How Water Hardness Affects Fish:
Water hardness affects freshwater fishies in terms of osmoregulation. Since hard water has a higher concentration of salts than soft water, for example, the osmotic difference between the fish's internal environment and the surrounding water is smaller. In hard water, therefore, the osmoregulatory system has a reduced work load replacing ions lost from the blood. (The presence of calcium in the water also decreases cell permeability, which reduces ion losses and water influx). Conversely, fish in soft water need to have more efficient osmoregulatory systems and expend more effort to maintain their internal salt/water balance.
Water hardness also affects the regulation of blood calcium level, which also depends on diet. Hardwater fish cope with excess blood calcium by using an efficient system for excreting calcium, governed by a hormone called calcitonin. Softwater fish need to obtain more calcium from their diet and also use bones as calcium reservoirs to ensure that blood calcium levels remain constant.
Freshwater fishes have adapted to thrive in an immense range of water hardness values, from the soft acid waters of the Amazon river, with less than 50mg/litre calcium carbonate (3 dH), to the hard alkaline waters of the African Rift Valley lakes, with hardness values exceeding 330mg/litre calcium carbonate (18.5 dH). Within any particular environment, however, fish have tuned their physiological functions to cope efficiently with a fairly narrow range of water hardness levels and therefore osmotic pressure. Altering the hardness values outside this range or disrupting the major ion composition of water hardness will lead to extreme osmotic stress and other physiological malfunctions. As an example, if bicarbonate ions exceed normal levels then bicarbonate excretion by the gills fails, leading to an alkaline pH shift of the blood and symptoms of alkalosis. High bicarbonate levels also alter kidney functions, resulting in calciferous deposits in the kidney tubules. Fish eggs are also affected if they are put in abnormally hard water; they fail to 'harden'. This may sound contradictory, but the egg-hardening process involves the uptake of water from the surrounding medium so that the egg becomes turgid (i.e. hard); a higher than usual hardness level reduces the osmotic gradient between the inside and the outside of the egg and thus decreases the inflow of water.
Different fish species have a varying resistance to changes in water hardness, depending on their ability to alter their osmoregulatory process to changes in osmotic demand. Most fish can be acclimated slowly to abnormal water hardness. In general, however, they will be under unnatural stress and will not achieve optimum performance in growth, breeding, or disease resistance."
Emma
i have 10 mixed african cichlids 7 clown loachs and one pleco in a 55gallon tank i have lots of rocks and caves with a few live plants ...i keep my ph around 7.2-7.4 temp 80-82f and all is well sometimes at night i hear my loachs clicking so i know there really happy ...they all get along great and my loachs love hanging out with the cichlids all day so they are always out and about plus i feed them a large varity of food....i think what helped the most is that i got all of them all most at the same time and they where all babies and the loachs were bigger in the begging but now the cichlids out greww them but all is still well 
ireally appreceate every ones input like i said i just want happy healthy fish thank you again