Inherited 3-yr-old tank, fungus and dropsy

[Akuinnen]

6 months ago, my friend gave me her intact 3-year-old, 10 gallon tank with a high-quality filter and one plant. It also had one Siamese Algae Eater, bamboo shrimp, zebra danio and two cardinal tetras.

Over the last 6 months I've added about 5 more plants, a betta, two danios, and two tetras. However, I didn't understand how to cycle or test for cycling, so I added multiple plants in one day, and four fish in one day. (I had assumed the tank would be cycling since it was so old.)

Everything seemed fine until recently. One 3-yr-old tetra died right away, but had been looking sick before I got the tank. The other old tetra died of what looked like old age months later. Neither had visual signs of disease, their color just gradually faded. However, the 3-year-old danio got dropsy a week ago and had to be quarantined, and now two of the newer fish have white fungus on their fins.

I really want to know what I'm doing wrong! Only the old tetras and danios have died, but I'm worried about the new fish. I do a 30% water change every 2-3 weeks, and I feel like I'm slightly overfeeding. However, about a month ago a friend took care of my tank for a week and massively overfed the fish, causing a huge amount of algae growth. This was also a couple weeks before the fungus and dropsy showed up, so I think they may be linked.

Today, I moved the betta, algae eater and shrimp into a 2 gal tank and used Jungle Fungus Clear in the 10 gal. Are there any other changes I should make? How often should I change the water of a (hopefully) cycling 10 gal, and how do I know for sure if it's cycling?

Sorry for the long post, but I could really use some help!

[LadyVictorian]

One big change, do a 20% water changed every week....with a 10 gallon it needs to be cleaned and vacumed once a week.

[Akuinnen]

Thanks for the reply, I'm sure water changes was part of the problem. I've never gotten a bad reading when testing the water, but it's been over a month since I tested it. Maybe unclean water and my friend's extreme overfeeding caused the problems? (He dumped in probably two months worth of food in just a week!)

I'm still curious though, how do I know if this tank is cycling, or if there might be an ammonium spike, etc? And is Jungle Fungus Clear a good way to treat fungus?

[LadyVictorian]

I would also buy a new filter cartridge and start cycling over again. You have to test the ammonia and Nitrate levels. Once there is 0 ammonia and at least 10+ nitrate then you know your tank is fully cycled. Nuke the whole tank, clean all the decor in hot hit water and clean the tank with a bleach solution and rinse rinse rinse rinse.

[Akuinnen]

Thank you so much for the help! I'd forgotten about changing the filter cartridges, and mine looks like it's pretty old. Right now I have my carbon in a separate jar while the fungus clear is in the tank, but as soon as the fungus clear is done I'll change the cartridge. I'm a little worried about making too many changes at once though, what would be a good way to do it without stressing the fish?

[GoodMorning]

You should be fine with changing both the water and cartridge at once, i've done it plenty of times with no ill effects. But, if you are really anal about it, change the water first, then change the cartridge a couple days to a week later.