Cycling

[altivo]

(Not with a bicycle, either.)

So this morning, about eight hours after reassembling the tank, it looked good. The fish were active, and quickly ate a little food when I added it. The pH had risen slightly, but was acceptable. Then an hour later, while we were eating breakfast, we watched the tank "bloom" with bacteria so quickly that it soon resembled milky water or household ammonia. Literally fogged up so you couldn't see the fish.

This is apparently a bloom of heterotrophic bacteria, the ones that usually break down organic waste and produce ammonia. Oddly, we have just removed huge amounts of organic material from the tank, so it is almost like new, and I didn't expect this.

Then when I got home from work, I found that the other tank, the one with no fish in it, has bloomed as well. Whatever we did, it stimulated these little bugs to go wild. They reproduce faster than you can replace the water, so changing water doesn't do much to stop them. Mostly you just have to wait them out. They have switched from anaerobic to aerobic metabolism, which means they can use up a lot of oxygen from teh water so we put the power head back in there to provide additional aeration.

It occurs to me that I could add some chlorine to the fishless tank to clear the bacteria, but of course it would take the good ones along with the bad, and that's not a desirable thing to bring about.

So we wait, watching the pH and ammonia levels and changing water if necessary to keep those controlled.

Comments

[deffox]

So, do you use a gravel siphon?

I find they are the best way to keep the gravel gunk under control. If the tank has gone a very long time without siphoning the gravel it will kick up a large cloud, but if done regularly it works well. Back when I had fish I would siphon a five gallon bucket out of a 30 gallon tank every week or two. That quantity would allow me to clean approximately 1/3 of the gravel per cleaning.

The large siphons work better than the small ones at preventing gravel from being pulled into the bucket.

[altivo]

Yup. I agree and we do use a gravel siphon regularly. Since the large tank was completely cleared of fish and decorations so we could remove the undergravel filter plates, and that kicked up a lot of gunk, we siphoned the gravel very thoroughly after that and replaced almost all the water. No doubt these bacteria sprang from the gravel, though. That was the only possible source. Hopefully the aerobic Nitrosoma bacteria are still there and will take over in a day or two as they should.

The risks are depletion of the oxygen supply, which we are trying to prevent by additional aeration, and a sudden build-up of ammonia. Aeration should help get rid of some ammonia if that happens, but we need the "good" bacteria to start converting it to nitrates.