Aquarium Challenges : Trouble in the Tank

I guess it's been about 2 months now since I started the aquarium, and we've had a few challenges recently... After the third neon tetra was eaten by the goldfish, I have removed the other 2 to a separate tank, set up in the kitchen. This was also my emergency aquarium in case the second swordtail (my daughter has named her Comet because of her black tail) had babies, which we believe the orange one (Crystal) did. But still waiting for that event, if it will come at all.

Although Crystal acted fairly normal, she stayed skinny. I began to suspect something was wrong. Then a couple of days ago, she seemed to lose interest in eating, was at times along the bottom of the aquarium, or right in the thick of the plants, which is where she died.

The male swordtail has worried me today, he is hiding behind one of the plants, which is not his usual behaviour. So I'll keep an eye on that.

The goldfish seem always to be hungry. The little faces pressed against the glass as I pass by, began to be a bit disturbing rather than charming. My husband reported that the fish in the dentist's office seemed almost disinterested when they were fed. In contrast, some of mine (the 3 white & orange "feeder" goldfish) would break into fights, bumping & chasing each other. So I increased the size of the feedings and increased from 1 or 2 times to 3 times per day. But after a few days, the water turned cloudy (since a greenish colour, apparently an algae outbreak). So I cut back on the feedings again, and kept the light off (I had been leaving it on during the day, mainly for the benefit of my aquarium plants), and cleaned the filter more often, and within a few more days, it cleared up. But I've kept them on the reduced feedings (usually only in the morning) ever since.

On a brighter note, the aquarium plants seem to be doing fairly well, and one of them is showing visible new growth. The pleco has stopped hiding under the filter (ever since the time I had to push him off, in order to clean it), choosing to instead hide under the plants where he is invisible. Occasionally he comes out during a feeding, which is a real treat to watch.

PS. The photo is not mine, it is a Microsoft clip art, but seemed relevant to the topic. ;-)