Overfeeding again?

Question
My dad has a 10gal goldfish tank.  When he first set it up, he was having a problem with overfeeding and most of the fish died.  The food was clearly rotting on the bottom, so the solution was obvious: feed less.  A successful year later, he now has lots of fuzzy white puffs floating along the bottom of the tank, one dead fish, and the scales of another fish have darkened, as if tarnished (the rest of the fish look fine).  I can only guess the puffs (which he describes as slimy when he tries to pick them out) are a mold of some sort, but he showed me how much he feeds, and it seems to me absolutely within reason.  (I keep two tanks myself and have never had either problem.)  I also don't know what could have caused the one fish's discoloration.  Any ideas?  I want to point out that he has cloth - not plastic - plant decorations.  I'd never seen that before, so wonder if something like that complicate cleanliness?  Also, he has only a thin layer of gravel on the bottom.  Could that hinder uneaten food's ability to decompose properly?  He is meticulously attentive to this tank, keeping a log of every cleaning and water change, so I know his concern is genuine...  Thanks for any help you can provide!

Answer
Hi Kim;

Poor guys. You didn't mention how many goldfish are in there are or how big they all are, but it sounds like there are at least 4 and a ten gallon is just not enough room. They need a much larger tank and larger filter. The tank has ammonia problems from overfeeding and overcrowding so it will continue to be toxic in there until they are moved to a bigger one. Black that appears suddenly on goldfish is from ammonia burns. The white stuff is caused by a bacterial/fungal growth trying to consume decaying food. Once the ammonia began to climb to lethal levels, the fish didn't feel very good so they probably slowed down eating, which left even more excess food to rot.

To keep them alive until a bigger tank is ready, they need a 25% water change every day for a week. Also vacuum the gravel to get rid of the excess waste and food, which is one of the causes of the ammonia. Once the ammonia is looking better and the white stuff is gone, just do a 25% change every 2 or 3 days to keep the toxicity down to a minimum. Cut back on food and only give them a very small amount.

Goldfish are very messy fish that get BIG (6 to 8 inches) so each goldfish needs 10 gallons all to itself. They are probably bigger now than they were at first so they are adding even more waste to the system. It's only going to get worse as time goes by, if they survive the coming days.  

Ammonia comes from two main sources in fish tanks; Fish waste and excess food. A third common source is dead fish so the one body probably contributed a bit to it as well, even if was in there for only a short time. Fish waste is a normal part of keeping aquariums and is expected to be handled by the system. Excess food is not. There should never be any leftovers to fall on the bottom in any tank. We all overfeed from time to time, but we have to clean up after ourselves so it doesn't hurt the fish. When feeding fish, only give them enough to consume it from all areas of the tank in five minutes. Feed them once a day and remove anything that sits on the bottom, feeding less next time until you can find a good amount that works.

Shallow gravel is just fine, and it is actually best to keep it as shallow as possible to avoid waste build-up. It is not the job of our tank's beneficial bacteria systems to decompose excess food. It is OUR job to avoid overfeeding in the first place.

It would be good to get test kits for ammonia, pH, nitrite and nitrate. You need at least an ammonia test kit so you can monitor the levels as water changes are made to be sure it is keeping it to tolerable levels. Here is a link to a good article on test kits, why they are such good tools, and what to do with them;

http://faq.thekrib.com/begin-tests.html

Below is a link to my page about "new tank syndrome" to help you know more about getting through the break-in period in the new tank. Also, some site links to help you know more about goldfish, feeding, and tips for new tanks;

http://www.xanga.com/Expert_Fish_Help

http://www.firsttankguide.net/goldfish.php

http://www.netpets.org/fish/reference/freshref/goldfaq.html

http://www.goldfishinfo.com/feeding.htm

http://www.bellaonline.com/articles/art28815.asp

http://www.firsttankguide.net/steps.php

http://www.thetropicaltank.co.uk/bcycling.htm

I hope they feel better soon...

At Your Service;
Chris Robbins