I added a heater to this tank like a month ago and thought nothing of it. Guppies and Heterandria formosa are both tropical-esque fish. H. formosa is Florida based. And yes, the H. formosa do seem to like it in the heated tank. I still see some swimming around. But for some reason the ricciocarpus natans absolutely hated it. I just noticed right now that it's all disappeared. I don't see any in my unheated 10 gallon, either, which is a little strange. Huh.
Good news! I solved the mystery of the disappearing ricciocarpus natans: it was the lighting.
Around the same time I added the heater, I also decreased the number of hours the lights were on in an attempt to thwart my arch nemesis, cladophora algae. It worked, so I decreased the lights lower and lower (and as a result had no algae). At one point the lights were on as little as eight hours a day: three in the morning before I left for work and five in the early evening after I got home.
So. Here's how I figured out that wasn't enough light for ricciocarpus natans:
About two weeks ago I thoroughly washed out the paradiso synthetic sea sponges that I use in my hang-on-back waterfall filter. Thoroughly, for several days in a row, with tap water. On the plus side, my water went from murky particulates to crystal clear. On the down side, there was an ammonia spike soon after. I guess the lighting schedule wasn't allowing enough plant growth to clear all the ammonia, and the tank slowly but surely had acquired a substantial beneficial bacteria population in the filter sponges. Normally it wouldn't have mattered if I had washed the sponges out like that, because my previous lighting schedule of 16 hours a day led to the plants vastly outcompeting the bacteria in ammonia consumption. But, as I found out, the bacteria had been doing a lot of the work. Four or five female guppies died. None of the male guppies died and none of the heterandria formosa, but female guppies are weak right when they're giving birth and it was the older, heavily pregnant females who succumbed.
My solution was to leave the lights on for a week, until the tank stopped smelling (did I mention I'm lazy?). It worked, and no more fish died after that first day I had the lights on. But there were side effects. I'm not seeing all that much algae. The plant growth, though, was explosive. And the ludwigia repens, one of our native plants that can be green or red, turned a lovely bright red under the lights. It's very pretty now. Also, some three or five little duckweeds that had gotten in the tank recently doubled and tripled, and it was up to me to hunt them down and take them out. Which leads us to the very rambly end of the story: As I was removing duckweed from the tank just now, one by one with my planting tweezers (I hate duckweed, it has no resale value), I spotted.... two happy, dividing little ricciocarpus natans! ha ha! It wasn't the temperature after all; the heater's been on this whole time. It was the light. My conclusion is: although I had been about to reset the light timer to its normal eight hours a day now that this ammonia spike has passed, I am instead setting it to 12 hours a day, out of respect for the plants in the tank. yay, the ricciocarpus natans survived
Edited by EricaWieser, 03 May 2013 - 05:59 PM.