It is obvious to most people that aquarium filters capture the gunk suspended in the tank’s water, leaving it looking clear.  This is called mechanical filtration.  Filters perform a much more important function, however, called biological filtration.  As discussed in the post on cycling an aquarium, fish produce ammonia both directly and through the decomposition of their waste.  Ammonia is toxic, but the cycling process builds up a colony of bacteria that consume the ammonia to produce nitrite.  The nitrite is even more toxic than ammonia, but is also consumed by bacteria to produce nitrate, which is much less harmful.

Filters perform the important task of moving water that contains ammonia and nitrite past the colonies of bacteria.  Insufficient movement of water can result in a toxic build up of ammonia or nitrite, which can’t be processed quickly enough.  This mostly happens in tanks that are overstocked with fish or over fed with too little filtration and water movement.

I worked from home this past Wednesday, following my normal routine – get up early, go to the gym, come home and get on a conference by 8am.  Somewhere between calls, I make the rounds to turn on my aquarium lights and feed the tanks.  When I walked into my family room and turned on the light, I saw a horrific sight…  Nearly all of my fish were laying dead on the bottom of the tank.  That was heartbreaking.  My prized 4 year old angelfish, named “Tailfin” was among the dead.

There was no indication of what happened – the fish were fine when I had turned the lights out the night before.  3 young angels and a pleco survived, so whatever happened could not have been totally devastating.

I perform 50% or larger water changes weekly, and have for years.  I vacuum the gravel thoroughly each time.  It had been 3 days since the last water change.

Here is my theory on what happened:

The day before, we lost power in our house for about 20 minutes.  Not terribly long.  I have battery powered air pumps that turn on when the power goes out.  All of them came on, except one – the one in the 55G tank where the fish died.  I replaced the batteries, but it didn’t work.  I noticed that if I took the hose off, it would very slowly work.  I hooked the hose up again and had to go take a phone call for work.  In the mean time, the power came back on.  When I finished the call an hour later, I walked into my family room and the battery powered air pump was pumping normally – because I had forced it on whilest trying to get it to work earlier.  I turned the pump off and didn’t think about it until the next morning, when I found all of the dead fish.

Upon inspecting the air pump, there is a think tar/oil like liquid that appears to be oozing out of the air outlet.  My suspicion is that water from the tank had somehow siphoned through the air line back into the pump where it sat for many months.  The reason the pump didn’t work at first was that it was gummed up with this likely concoction of water, oil, rust, etc.  Eventually, the pump pushed the goo out and up the air hose and into the tank.

What I can’t reconcile is why the fish did not start having trouble the night before – 9 hours after the pump was turned off, and presumably after the goo was put into the tank.

So, that was extraordinarily sad for me, and I will try to learn a lesson from it.  I have decided to re-populate the tank with African cichlids, using the opportunity to try something new and challenging.

I will post pictures as I can.

Here are some pearls of wisdom I wish I had when I was starting out with my aquarium.

Starting Out and Buying Aquarium Stuff

Accept that you are going to kill some fish on accident.  You will either learn from the mistake or drop the hobby.

New Aquariums need to be cycled.  Taking the time to understand what this means is a must.

Small tanks are not easier to keep fish in than large ones.  Maintenance on a small tank takes less time, but a larger tank provides a larger volume of water which generally provides a more stable environment for fish, and is more forgiving of mistakes by beginners.

Under-gravel filters suck.  You will hate them.  Also see the comment on gravel.

Unless you have a specific need, don’t put gravel in the bottom of your tank.  Go with a “bare bottom” tank, and add decorations.  Leaving the tank bottom bare will make it easier to clean out the fish waste.  If it is not kept clean, it will contaminate the water, causing sick and dying fish.

Do not buy fish on impulse.  Read up on fish that you are considering buying.  Many small and cute, colorful fish in the pet store grow up to be demanding monsters.

Don’t rely on the tank size rating when buying a filter for your tank.  Most filters are rated on their flow without media, which will slow down the flow.  You want filtration that will turn the water over between 5 and 10 times per hour.  For a 10 gallon tank, that’s a 50 to 100 gph filter.  For a 55G tank, it’s 225 to 550 gph.

Canister filters are well worth the extra money.  They are quieter and more powerful than the kind that hang on the back of the tank.

Maintaining a planted tank is much harder and more expensive than it looks

Spend the extra money and get a “master test kit” to test your water with (this is the kind that uses drops of reagent chemicals in test tubes).  The test strips are not that reliable.

Online pet stores are MUCH cheaper for most food, chemicals and hardware.

Pet stores regularly sell fish that are entirely inappropriate for 99.9% of fish keepers.  Know what you are buying and whether you can properly care for them.

The employees of pet stores only appear to know what they are talking about.

Don’t accept the advice of pet store employees on setting up a new tank, particularly the big chain stores like Petco, Petsmart, etc.

Don’t accept the advice of pet store employees on how to treat a disease with your fish

• Pet store employees have a medicine to sell you to cure just about anything you can come up with.  The trouble is, medicine can rarely cure the cause of a problem. Read the rest of this entry »