It seems that we have a lot of koi keepers who need, for one reason or another to bring some of their fish in during winter months. Sometimes they find a sick fish in their pond that needs treatment, or sometimes they just want want to keep some of their best fish in for the winter.
Because Cyprinus carpio (koi) are cold water fish, many people chose to maintain water temperatures below 60* F. While the low temperatures used (50* F – 60* F) are somewhat dangerous for koi, is very doable provided the fish are in good health, not overcrowded, and the filter is 100% cycled. The real danger comes when the biological filter is not totally up to snuff before it is exposed to colder water. This is because of the different reproduction rates of the two types of bacteria responsible for oxidizing nitrogen.
Because biofilters take a very long time to cycle in water below 70* F many people use ammonia binders such as Amquel to mitigate its dangerous effects. When ammonia bound up by Amquel. It’s not toxic to fish, but is still indirectly dangerous because it needs to be converted to NitrIte, which cannot be controlled by ammonia binders. While it is true that salt helps control the NitrIte problem to some extend, it is really only a bandaid, and does not work when NitrIte levels are very high.
For folks who are dealing with cycling a filter in colder water, I suggest two things. First, filters in cool water need to be quite large, so we often need to add to the filtration. A simple way is to drill a bunch of holes into the bottom of a 5 Gal bucket, fill it with lava rock (stones for gas grills) or plastic kitchen scrubbies, suspend it above the tank, and feed it with a sump pump, letting the water trickle through the media, and drain out through the holes, back into the tank. Try to distribute the water evenly over the top of the media. Making a spray bar out of tube or pipe with holes drilled in it helps with this. Try to size the pump to turn over all the water in the holding tank 4 to 5 times an hour.
Next we need to get some bacteria in there. Nitrosonomas are the bacteria that first convert Ammonia into NitrIte and then another type of bacteria (Nitrobacter) takes over and converts the NitrIte into fairly harmless NitrAte. The problem is that Nitrobacter divide much more slowly than Nitrosonomas, and our fish have to live with NitrIte much longer than Ammonia throughout the cycle process. They will also divide much more slowly, or even not at all in colder water.
When the water temperature is low, we find ourselves in a bit of trouble. We need to keep the water temp down, and the Ph low to mitigate the toxicity of the Ammonia, but our Nitrobacter will either develop slowly or not at all under these conditions. Nitrosonomas will convert all the Ammonia to NitrIte, but Nitrobacter will never come along to detoxify the NitrItes into NitrAtes. NitrItes will spiral out of control, and the fish will suffer no matter how much salt is added.
So, we need an instant cycle. I’ve always thought how great it would be if someone kept a bunch of cycled filter material around to send off to folks facing this kind of problem. I keep planning to do it myself, but my wife can’t stand it when I run pumps all over the place. We always take our bacteria for granted, but it’s more precious than gold when you don’t have any.
I suggest everyone try to keep some live filter bacteria around at all times.
If not, one company bottles it up and sells it. They only ship overnight, with their product on cold packs. This is the ONLY company I know of that sells such a product, and it is NOT cheap! If you can find a person or company with healthy fish that can ring out their filters for you, that would be the best option, but if not, Fritz Pet’s Turbo Start is your best Option. It is also worth mentioning that, at least in my experience, Bio Spira from Marineland does not work.
No matter how you get the bacteria, you need to do a few things before you add it to make sure it works. If you get the bacteria from another person’s filter, you will need to remove all the fish for a couple of hours after dumping it in, or they will die. You can add them back in once the water becomes more or less clear.
1) Keep your existing filter running, and add the new one.
2) Doing hourly water changes, bring the Ammonia and NitrItes down to less than 1ppm.
3) Use a phosphate-based neutral Ph buffer. You could use baking soda, which usually holds the Ph around 8.0, but for cycling I suggest something that will hold it closer to neutral (7.0). I like Seachem’s neutral buffer because it holds the Ph at 7.0, which makes any Ammonia spike less toxic than it would be at 8.0. Either way, both types of bacteria require a Ph buffer to divide.
4) Add the bacteria. Don’t forget to remove the fish if you obtained bacteria (gunk) from someone’s filter.
5) Bring the temp up to at least 76* F. A 300 W aquarium filter should work for this. Make sure not to bring up the temp too fast or you will shock the fish. If your temp is still in the 60’s, you should be able to bring it up to 76* within 24 hours safely. You can let the temp fall again once the filter is cycled.
7) Keep a close eye on your Ammonia and NitrIte levels. I’ve done this a number of times, and the Ammonia usually rises to 1.0, and then drops. NitrIte then comes up to .5, and then drops. I’ve also done it, and never even seen Ammonia or NitrIte. With high stocking levels, I would expect to see a slight spike in both.