Hi all - First time poster here, and I'll try to do this right. Forgive me if I don't know the proper lingo.
I was given a fully populated and settled 30 gallon freshwater tank about eight years ago. The person who gave it to me had it for at least five years before that, and at the time he mostly had tetras, plus one mature Australian Rainbow.
We now have two panda corey, two Siamese algae eaters, five assorted tetra, one sole surviving shrimp, ramshorn (I'm pretty sure) snails (it took awhile, but they have achieved balance and don't overpopulate), and the above mentioned Australian Rainbow. We also have live plants like Amazon Sword, water lettuce, Vallisneria Spirallis, and something I'm pretty sure is alternanthera. We haven't added new fish in about a year, and we haven't lost one in about the same amount of time. The Siamese and pandas are at least six years old. The rest somewhere between two and five.
We recently got some Java Fern from a friend, who hasn't mentioned any problems with her tank. I didn't think to rinse it before putting it in my tank, and will check on things like that in the future.
About a week or two after we put in the Java Fern (which is the only change I've made), the Australian Rainbow stopped eating. This happened once before, about a year ago, but it (he?) started again and seemed to have no ill effects. But it's been five days, and though he's active and moves around when the flakes or pellets are put in, and sometimes opens his mouth like he wants to eat, no food is actually going in. Today I tried frozen blood worms, as that's always been a favorite, and though he did get very active, he didn't eat.
I change out about 1/3 of the tank water and vacuum about every three weeks. I also add fresh water every time I notice an inch or two of evaporation. This has been the case for the entire time I've had the tank. I could be better about cleaning the filter (an AquaClear filter for 30+ gallon tanks). But that happens about every three weeks as well. I add Seachem Florish Excel Bioavailable Carbon every day, plus Seachem Florish plant tabs every three months. I add API Prime with every water change.
I don't know the tank parameters. I'm not great at that kind of thing and have figured that as everything is staying alive I must be doing something right.
The temperature is set at 79 degrees and I've got full spectrum lighting that's on for 13 hours a day. The tank gets no direct light, but plenty of ambient light.
Any thoughts on why my Rainbow won't eat?
Thanks for any assistance!