My tank what am I doing wrong???

Question
Hi I own a 40 Litre Jebo R 338 R-Style Aquarium Electro-Switch tank, I set it up in September 2008, I had 4 small goldfish, 3 zebrafish, 2 other small fish ( I can't remember their names) and a Siamese fighting fish (cold water). Recently they have all died except for the fighting fish & it's really sad because they belonged to my little 4 yr old boy (b'day present). I have noticed that the PH levels weren't so good recently and I tried to correct them also I cleaned out the tank (half of the water)& replaced it with clean fresh water (I use a dechlorinator). i try to clean out the tank once a fortnight. I also removed live plants as they would seem to get mouldy quite quickly? When I got the tank (brand new) it came with no instructions about maintenance of the tank as in when do I clean the sponge filter at the top & the filter rocks, how much water do I take out? do I take the fish out and completely drain the tank and clean or what? I'm basically lost and feel terrible that these little fish are all dying, I would really appreciate some help as I want my little boy to enjoy his gift and not wake up finding his fish dead. Even if you could suggest a book I can purchase with relevant info. I live in Australia and it is winter would that have anything to do with it? I don't know??? Thanks for your help.

Answer
Hi Julie;

I'm so sorry you've had such a bad experience. Hopefully we can get your tank back on the right track. Just leave the betta all by himself for now and make a 25% water change once a week. That's normal maintenance for any aquarium. Leave him in the tank for water changes. More about what to do with your filter and other things below...

There are several problems with your tank and fish actually, mostly regarding tank size and fish compatibility. There are some basics you need to know before you get any more fish or before doing anything else to your tank. You can actually do your research right here on the internet. I will give you some web page links at the end of this letter to help get you started.

The first problem I see is that a 40 liter tank is far too small for 4 goldfish grow up in at all. They probably had become larger over the past few months and just pushed the system over the edge. Your little tank is okay for just one goldfish and no other fish for awhile but one goldfish requires at least 40 liters all to itself, more like 60 at least as it grows to it's adult size. Goldfish grow to be very large (15 cm and larger) and are very messy even while still small. A good scenario for a goldfish tank is 80 liters for your first goldfish and then another 40 liters for each one after that. This means you would need at least a 160 to 200 liter tank for four goldfish to even begin feeling comfy and healthy on a long term basis.

Another problem you have had is with water quality and water chemistry. It is best not to try to alter the pH with additives or chemicals. Your fish are accustomed to what the pH already is. Trying to change it by adding stuff to the tank causes fluctuations that are very stressful to the fish and to the plants, as well as to the biological balance in the tank in general. What we want for our fish and the system is stability, not an exact reading on a chart that says it's "okay" for our particular breed of fish. The fish we buy in fish stores are all kept in one source of water that the store used in all their tanks anyway. The fish charts and care profiles that have pH and water hardness recommendations are referring to the water that the original breed in their wild environment was exposed to. Most pet fish are farm raised and have never seen those environments. Or, they've been in captivity long enough that they've already adapted to what our water here is. They've adapted to what we keep them in. To keep the water chemistry healthy and stable, including the pH, simply requires a weekly 25% water change. Changing water only every couple of weeks or more, especially a large amount (over 25%) can seriously shock your fish. After your fish have been living in the tank water for awhile, especially in such crowded conditions, it becomes different in chemistry and of course in quality as well. Regular maintenance once a week is the key. Leave the fish in the tank to make a water change. It is actually more stressful to take them out and put them in again. Just work your way around them to siphon water from the bottom and vacuum out crud. They will get used to the process. Just make sure to use a water conditioner and make sure the new water is the same temperature as the tank water so your fish don't go into temperature shock.

Filter maintenance is very simple. Rinse the filter pad(s), bags, carbon, etc., in a container of tank water to release the crud that plugs them up. (Throw the dirty rinse water away.) The filter media is a home for the beneficial (good) bacteria that consumes fish waste toxins. Only replace filter pads when they can no longer be rinsed well enough to let the water flow freely again. Or, replace if they are literally falling apart from age. I have some filter pads that have been in use for years. If the filter pad is removed, out goes your beneficial bacteria colonies and up goes waste toxins, making your fish sick or causing death. Beneficial bacteria colonies also grow on the decorations and rocks. Disturbing the decorations and rocks too much or removing and cleaning them can kill too much of this important bacteria off. It can take weeks for your system to fully recover, depending on the "bio-load" in your tank. The bio-load refers to how many fish, the types of fish, how much and type of food, etc. Basically anything biological going into or living in the tank affects it's bio-load.

Now for the compatibility problems...

Temperature - Bettas (Siamese Fighting Fish) are actually a tropical fish that needs a water temperature over 76f all the time. He needs a heater in his tank if you don't have one already. Your goldfish and zebras were cold water fish that need water temperatures below 72f all the time.

Future size of fish - Even though the zebras and goldfish are both cold water fish, they should not be in the same tank together. Goldfish can very quickly grow large enough to eat the little zebras. Your goldies should have been large enough to eat them if you had them all for several months. But, being in crowded tank conditions may have slowed their growth.

Those are the main problems that I can see but you will need to know more so here are some web page links (in no particular order) to help you with your tank;

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

http://www.aquahobby.com/articles/e_waterchange.php

http://freshaquarium.about.com/od/aquariumstartup/u/gettingstarted.htm

http://fins.actwin.com/mirror/begin-intro.html#success-tips

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

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

http://freshaquarium.about.com/od/aquariumstartup/a/newtankmistakes.htm

http://www.fishprofiles.com/profiles/default.aspx?pnl=fresh

Let me know if you more questions or need more help...

At Your Service;
Chris Robbins