Okay, what pops out at me right away is that your pleco was stressed by being put into a tank full of cold water. Is your pet store a specialty tropical fish hobbyist store, or is it just a general pet store? Most tropical fish hobbyist stores keep their ambient air temperature pretty high–it saves on having to heat all those fish tanks. So your pleco may have gone from a comfy 78[sup]o[/sup] to a frigid and uncomfortable 70[sup]o[/sup]. No wonder he’s stressed and came down with ick. Also, a couple of messy 3 inch goldfish are going to make tank water conditions less than ideal. So you dropped him into cold, dirty water (at least by the standards of his former home in the pet store).
Second point: what exactly do you mean by a “carbon filter”? Is it:
A. A hang on the back power filter, with a blue fuzzy pad glued to a hard plastic frame that you slide up and down? Or with a white plastic sponge that sits by itself in a holder, or a white fuzzy pad that fits over the plastic frame?
B. A plastic box that sits on the bottom of the tank, and you fill it up with pieces of charcoal and filter floss, and air from an air pump bubbles through it?
C. Other? Brand name? Physical description? Do you have an undergravel filter, too?
“B” is hopeless for anything bigger than guppies.
Next point: your oh-so-helpful pet store worker is only there to sell fish. Sorry. He gave you bad advice, IMO, to add an algae eater to your goldfish tank to control algae. The only thing that really controls algae is to have video fish. Otherwise, just feed sparingly and, like I said, resign yourself to having to scrub the tank every so often.
Also: “pond-like conditions”? You mean the water itself turned green? This is not something an algae eater of any kind can help you with. Number one cause of green water–overfeeding. (see below)
A fish tank is an artificial environment. Aquarium books pay lots of lip service to the concept of a “balanced tank”, but in actual practice this is impossible. For one thing, the unfilterable waste products do build up and you do have to take out the bad water and put in the good water.
So you’re always gonna have algae. Just a fact of life.
Next point: a half-teaspoon of goldfish flakes is WAAAAYY too much. :eek: A fish’s stomach is about as big as his eye. Visualize, for each fish, enough food to cover his eye. And that’s it. Muster up every bit of self-control you have and DO NOT FEED THEM AGAIN. No matter how prettily they swim up to the front of the tank and beg.
Next point: A 10 gallon tank is IMO not really big enough for 2 three-inch goldfish, especially fat ones like Moors and fantails. The “one gallon of water per inch of fish” rule only really applies to tropicals, with their skinny bodies and low waste output. Goldfish, as I said, poop a lot, and in addition they excrete ammonia (which is toxic) through their gills. If you don’t want to go to a bigger tank, I’d stick with 25 cent Wal-Mart goldfish, say 3 or 4 of them, each about an inch and a half long. They will last about a month or two, and then you go get some more.
It is true that goldfish don’t tend to outgrow their tank, that they tend to stay the right size. (Nobody really knows why this is, but they think it’s something to do with waste products.) Anyway, this only applies when you start out with really small goldfish and let them grow into their tank. Then they’ll come to an equilibrium, with their own waste products, and the amount of food you’re giving them, and the frequency of water changes that you’re doing.
But just starting off with a couple of 3 inch goldfish, well, like you just found out, that’s about the total possible population for a 10 gallon tank, and when you added the pleco, you added HIS waste load to the equation and upset the equilibrium.
Next point: A 70% water change is way too much all at once. You should change only 10% to 25% of the water at any one time. Reason? It alters the pH and changes the equation.
So, what I would advise you is to decide what you want to do. I don’t think your little piscine menage a trois is going to work as is. The ick remedy, by itself, isn’t going to accomplish anything except make you feel like you’re doing something. You have to fix the underlying problem with your tank conditions.
Are the two goldfish still alive? If so, and if you don’t want to get a separate tank for the pleco, what you can do is scrap the pleco and just go with the goldfish. Or, you can scrap the goldfish and try to salvage the pleco by buying him a heater and doing 10% water changes every day (correcting for pH, of course) until he gets better. A 10% water change is only one gallon of water.
Or you could go buy a 20 gallon tank and a suitable heater, and a power filter one size bigger than recommended on the box for a 20 gallon tank, and try to salvage all three of them. Tricky, but possible. The only limitation is your wallet.
How to humanely kill a fish: Scoop him out and put him in a Tupperware container full of tank water. Put a lid on it, so he doesn’t jump out, and put the whole thing in the deep freeze overnight. His metabolism will just go slower and slower until it finally shuts down.
Long term advice: I strongly advise you to get smart and start reading. Go down to the library and check out everything they have on fishkeeping. Also, the mind boggles at how many websites there are on fishkeeping.