Farlowella: The
F. acus is probably not actually
F. acus. This species is very rarely exported and in fact is now a highly endangered species because of destruction of its natural habitat for farming or ranching and I don't remember what all. According to my research,
F. vittata has been regularly exported and usually called
F. acus which is very similar in appearance. There are some photos and text on our Profile of
F. vittata. I have three, "sold" as acus but obviously vittata or so I assume.
They do well in groups, I had one for several months that was fine, but I like this fish so much I decided to get two more. One looks thinner than the other two, so I'm assuming perhaps a male and two females; I can't distinguish the "bristles" on the rostrum which the male develops at maturity, but I don't know how long it takes for this species to mature or how old my fish may be. The three never seem to squabble (males sometimes do, though nothing serious). It would be neat to have them spawn; it is not that difficult.
Speaking of spawning, I did the pwc today as usual, and in the 90g I moved the
Nematobrycon palmeri and N. lacortei over to the 115g. Which meant I was knocking over wood a bit. Afterwards, spotted half a dozen fry, about 1/4 inch long, grazing through the brush algae on one of the standing wood "stumps." At first I assumed it was the pencilfish,
Nannostomus eques, which are always spawning in that tank and a few times fry survive predation. But the shape was not quite right, and the colouration was different; after some looking around, I figured out it has to be the
Hyphessobrycon metae. These are very rare in the hobby, I've only once ever seen them in stores, and that was when I bought the seven I have in November 2008 from one of my lfs that carries almost exclusively wild-caught fish from South America. These were from the Peruvian Amazon basin.
Frogbit: throw it out usually. It is a funny plant, the leaves develop yellow edges quite a bit, I have some in my spare 33g with the top open (can't in the 90g or 115g or the hatchets would all be dried out on the floor next morning) but seems to be the same [thought it might be excess humidity]. I've changed ferts, back to Flourish twice weekly, and I think it was better today, so it may just need good nutrient fertilization. It grows very fast, as most surface plants do because of the plentiful CO2 from the air and the light right above. Anyway, when the weather warms up, I will send you some by mail. I sent some down to Stephanie in California but for reasons unknown the US Post took a week to get it there (my package of other plants to Texas arrived in 3 days) and it was dead. With our Priority Post I should be able to get it to you in 1-2 days, so when the weather is warm in Quebec, let me know. I don't have any insulation stuff for cold weather.
On the water change: the hardness in the tap water and/or tank water will buffer the pH. With my tanks at zero GH and KH, and my tap the same or maybe <1 dKH, the pH of the tank only goes up a few decimal points when I do a 50% water change. Not enough to cause issues. In your case, the replacement water will also be RO & tap mixed, so once you work out the proportions, you should have no significant changes. Keeping some hardness does help to prevent the pH lowering too far, as in my 115g, which is at 6.0 and with tap water at 7 it rise to about 6.3 with a 50% change.
Byron.