Cycling Your Aquarium – Myths and Facts

If I had a nickel for every time someone told me that they wanted that fish but they have to wait a month because they have to “cycle a new tank” I could have enough money to make yet another trip to Papua. I just wanted to give them a big Gibbs slap (NCIS fans know) but with a 2x4!

I guess this got to be all the rage on the interNut 10 or so years ago to do a freshwater fishless tank cycling, I really don’t know why. If you already have tanks set up at home and they are doing fine there is absolutely no need to take a month to cycle a new tank. It’s one of the reasons I yell at you to go find a local aquarium club, join it and attend the meetings. Club members all know their fish and they certainly don’t take 30 days to cycle a freshwater aquarium.

Since I was in the process of changing out a worn sponge filter in one of my tanks I decided to take a few pictures. Now this was a sponge filter that was in a bare bottom tank, no gravel. So ALL of the bio filtration or at least most of it was contained in the sponge filter. Yes there is a little bit of bio filtration going on in the biofilm on the glass and on any plant leaves that happen to be in the aquarium but that’s minor compared to the growing surface area for bacteria in a sponge filter.

I try to clean my sponge filters, whether in a bare bottom tank or a tank with gravel in it at least every other water change. Take it over to the sink and under “about” the same temperature water squeeze it several times. You don’t want to squeeze it until it runs totally clear because by then you’ve also rinsed out a lot of bacteria. But you don’t have to just give it a quick squeeze, get rid of some of that dirt that has been accumulating. You certainly don’t have to worry about chlorine wiping out your sponge filter. That’s another one of the irritating myths floating around on the InterNut. Do the test yourself to prove it really doesn’t hurt anything. IF you destroy too many of the bacteria they won’t be around to neutralize(chew up) the ammonia waste. If you kill too many of them then you should be able to see an increase in the ammonia value, right? So take a sample before the water change, right after the water change and 4-5 hours later. If you’ve really killed too many bacteria you will see a rise in the ammonia value at 4-5 hours. Also, [how do I know this?? :-)], if you clean that sponge filter WAY too well you’ll often see kind of cloudy water the next day. So clean the filter but don’t go overboard.

So for the worn out sponge filter (it was a round ATI Hydro-sponge type) I just rinsed it out, but not too much. In this case I rinsed it out in a quart bucket so that I could save the dirty water. After squeezing the water out of it I cut it in half and tossed half into the trash. I took the new sponge and after washing it under running water squeezed it many times in that dirty water to help pull in some of those dirt particles that also have bacteria clinging to them. I then put the filter back together but take that extra ½ of the old sponge and put it on top of the new sponge. When water is pulled thru the new sponge it also pulls thru the old one and also helps to seed it. I probably don’t need to go that far but hey you don’t want an ammonia problem and this, so far, is a no brainer way to keep the bio filtration going. After a week or so or the next sponge cleaning I just toss out that other ½ old sponge.

So how about that new tank that we want “cycled”? Well that bucket of grungy dirty water that we cleaned our filter in will work just fine. Make sure you use dechlor and remove chloramines and chlorines in your new tank and then just pour in all of that “gunk” into the tank. Yeah the tank will look murky but if you have a decent filter it will all be in either your sponge filter, power filter or both and should be clear fairly quickly. If you are not adding too many fish you can actually add them right away. People with multiple tanks have been doing this for years and chuckling every time they hear a newbie talking about cycling another tank. You can do this with bacteria from your sponge filter HOB filter or even gravel siphon waste from one of your established aquariums. If it’s your first tank, get some dirty filter water from a friend, who doesn’t have a disease in their tanks. Yeah don’t use a filter from a diseased tank. I would think that is obvious but in the world these days nothing seems to be obvious so…

Anyway “cycling” a new tank is quick and it’s easy. Obviously you don’t want to completely fill that tank on the first day but if you are moving over a small group of rainbowfish to a breeding tank this is just a few minutes of work, not a multi-day process.

Pictures below
Old sponge filter, rinsed and cut into two. Save one part to help seed the new sponge filter.