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Discussion Starter · #1 ·
How to build your own homemade bio reactor​
Before you begin to question my sanity, a bio reactor is just a fancy name for a place for good bacteria to colonize (the same bacteria that eat ammonia and nitrites). It works on the principle that the good bacteria thrives in an oxygen rich environment (see bioballs) and can help to facilitate an effective method of using one media to colonize good bacteria allowing for easier water changes, or complete cleaning of the tank without completely needing to re-cycle the tank. Well you may wonder why not just use bio balls or let the bacteria colonize in the filter material, but one of the main problems with that is your tank is constantly changing. Obviously you have to replace the filter material eventually. There’s also the theory that the good bacteria are most effective when it is “young” as opposed to build up and stagnant on a surface. This is where the bio reactor can help. Since the filter media is constantly moving around and coming into contact with the other pieces of material it allows the regeneration of new and young bacteria to constantly replace the old, thus providing much improved capabilities of the bacteria. Also the fact that it can be moved from tank to tank can provide many benefits for many of us betta owners.

It’s worth noting that this isn’t a “must have” and that you can’t cycle and filter properly without it. I just found it to be a very neat and interesting DIY project that seems to work very well for me. Since I built one for my 10 gallon I have not seen one ammonia spike no matter what I do. I changed 100% of the water at one point and after a few days of it running again the fish were ready to go back in. No ammonia to speak of. If that’s not enough….it just plain looks cool.

For anyone that might have concerns with this blowing Mr. Betta around I can say that it won’t bother them. Since the bubbles are self-contained in the bottle the force of the air won’t be enough to do more than ripple the water at the slightest. I find using an adjustable air pump works best so you can gauge how much water it’s moving.

Please note that this was not my idea. I found a video on youtube showing different ways to build this thing. I took what I saw and began building these. After building 5 or so this was the method that I came up with that I felt worked the best. So it’s sort-of my design, but not my concept.

Alright….lets build this thing​

First I’ll go over the materials needed for this project:
- Some Cotton swabs (Q-tips)
- Rubbing Alcohol
- Your bottle of choice. For 10+ Gallon tanks I recommend the Fiji water bottle. It’s thick and square so it works wonderfully for the bigger tanks.
- Some air tubing. Clear or black, your choice.
- Suction cups. I used some from petco. Came in a 6 pack.
- Paper towels
- Your air stone. Should look like the one in my picture (below)
- Something to poke your holes in the bottle. I used a pick to poke the initial holes in the bottle and then followed up with a slightly larger flat head screwdriver to wallow out the holes a little larger in diameter.
- Some decent scissors. I used electrical scissors but you shouldn’t need anything more than some standard utility scissors.
- Something to remove adhesive. I am using commercial grade label remover, but anything strong should work fine. Varnish, mineral spirits, etc. all work.
- Your air pump, obviously :p Size depends on the size of your tank. I used a dual pump to run dual bio reactors.
- Most importantly, you’re going to need your bio media. There are a few different media choices, but I recommend using K1 filter media since the entire reactor was built around this media. I have seen straws used before though so it’s up to you to experiment.
- Fine Grit sand paper

Alright, now that you have the necessary materials we are ready to move on to construction.

First thing you are going to do is make sure the inside of your bottle is clean. I just used hot water since it was previously filled with….well…water lol

Once the inside is clean you are going to want to clean the outside. Start by removing the label on the bottle. Once completely off take your paper towel and put a little of your adhesive remover on it and wipe off the adhesive that held the label to the bottle. Make sure to get it all off. Once you are certain that it is gone get a fresh paper towel and using your rubbing alcohol, clean the entire surface of the bottle. This will remove all the impurities left behind by the previous chemical.

Now that your bottle is clean you can move on to making the hole in your cap to allow the air tube to enter the reactor and seat the air stone. I took my pick and poked a hole directly in the center of the bottle cap. From there I remove the cap from the bottle and took my scissors and began to work the hole until it was just a tiny bit smaller than the diameter of the air line (you don’t want your substrate to get in there). When the hole was the right size I did the same from the other side of the cap. This helps to remove the plastic burs that accumulate and make the hole perfectly round and smooth.

Now you can feed your tubing through the hole and into the air stone. The air stone should sit perfectly upright on the other side of the cap.


126 Posts
Discussion Starter · #2 ·
Now comes the fun part. It’s time to poke the holes in the bottom of the bottle. These holes are where water will enter the reactor and go through the bio media. The force of the rushing air bubbles going up the bottom will pull water in through the bottom and expel it out through the top, along with the air bubbles. Your goal here is to try and put as many holes in the bottom portion of the bottle as you can without making it one big hole. Reason being you want as much water to enter as possible through small holes. This keeps the draw so minimal that it won’t disturb Mr. Betta but it will still be very effective. You want to keep to the bottom portion of the bottle so use my picture for a reference. I chose to use my pick and poke a pattern in the bottom portion, and follow up with the flathead screwdriver to widen the holes just a little bit more. Trust me, this part is no fun but the end result is worth it if you take your time.

Once you have poked your holes in the bottle and maybe a few into your hand you’re ready to get your fine grit sand paper and lightly sand the area with the holes you just made until they are smooth. This is just to help protect Mr. Betta further.

Once smooth as silk, you get to….you guessed it…poke more holes. YAY! This time we are putting the holes at the top of the reactor (or bottom of the bottle, however you want to look at it). With these holes we are looking to make them a little larger. Reason being the air bubbles are going to fight to escape the bottle. If the holes are too small the bubbles will accumulate inside, the media won’t “boil” correctly and get stuck at the top, or your reactor will keep floating to the top. What I did here was use my pick to poke a circular pattern. I followed up with the scissors to make the holes bigger. This took some time (mostly because I’m OCD), but it’s worth it to do it right. As you can see from my picture that I put holes all over the top of mine, even some towards the side of the top. I learned from experience that those on the lip of the top help some stubborn air bubbles get free.

FINALLY you’re done with the worst part :) So now you can take your sand paper and smooth out the top holes just like you did the bottom ones. Don’t worry though, these aren’t as important. I don’t think Mr. Betta will want to swim through a wall of bubbles :p

From here I once again wiped down the entire bottle in rubbing alcohol using a fresh paper towel and from there proceeded to rinse the whole contraption off in the sink using hot water.

Now comes the suction cups. Here you can get creative and do whatever it is you want, but I’ll show you what I did for anybody who follows this word for word. First I poked six holes on the back of my reactor on the flat surface where I would insert my suction cups. I used a 2x2 pattern. Then I took one of my suction cups and cut off about ¾ of the part that holds the airline tubing (see picture). Then I remove the remaining pieces that stuck out from the section that I cut, and after squeezing the remaining pieces together fed it through the hole. This allowed there to be two little pieces that opened up once it was fed into the hole just enough to keep the suction cup in place rather well. Rinse and repeat five more times and walla! Ready to stick :)

You’re on the home stretch. Your almost done :) From here you need to add your filter material into the reactor. I am using Kaldness K1 media (the media that the whole reactor was designed around). If you are using a different media then the rest of this paragraph doesn’t pertain so you can skip it. At first you are going to want to put just enough K1 media in there to cover maybe an inch of the bottom of the bottle. Reason being that the media needs to break in….literally. For the first week the K1 will readily want to float to the top until bacteria starts to settle in it. Once that happens you will start to see that the K1 moves very gracefully through the water. When you have added the correct amount of media to the reactor you can now screw on your cap and look at your accomplishment. YAY!

From here you just pick a spot in your tank to mount it. When mounting the bottle be sure to not mount it straight up. Mount it at a little of a tilt. This will help to get the media moving in the first weeks.
Then just install your siphon protector onto your tubing somewhere and hook it up to your air pump of choice. I would recommend using a larger air pump than you think you need. Have a 10 Gallon? Get one that’s listed for 20 gallons. It helps move the water and media a lot more effectively.

-Video of the Kaldness K1 that I have.

YAY! Congratulations! You’re all done :) Now turn on the pump and marvel at your new contraption that you built all by yourself.

I’m hoping that everybody who attempted to build their own homemade bio reactor enjoyed the process and hopefully will enjoy its usefulness in their aquarium. This is just one of the many methods of biological filtering that’s available for us fish keepers, but I thought of it to be a neat and newer approach to biological filtration. Hey you never know, this could be the next best thing lol.

Please note that the first week or so your media might not move as much as you think it should. Be patient. Just like everything else regarding fish it takes a little bit for the bacteria to colonize there. Once they do and the material moves freely you can add more K1 until you have a nice “soupy” consistency of K1 in the bottle. Also for people using smaller bottles try starting with less K1 than I did. You might have a little too much in there if your bottle is smaller.
For anybody looking for some mechanical filtration for smaller tanks you can get a thin piece of filter floss and wrap it around the intake holes on the bottle and hold it there with a rubber band. I can confirm that this is an effective method of getting some mechanical filtration in your smaller tanks.

Regarding this guide, I wrote this solely to spread the knowledge. I firmly believe that the internet is an amazing source for knowledge and constant learning and that there is no such thing as a dumb idea. This guide was a collective of many people’s ideas including mine so feel free to share your ideas, share this guide, etc. however you feel. I’ll try to keep updating this guide to make it better, and better as long as I can.

Happy Fish Keeping :)

(Ill have a video up soon of the K1 bio reactor I have in my sump)

126 Posts
Discussion Starter · #5 ·
Hey pretty cool idea! My only question is, wouldn't this be the same as a corner filter/boxfilter?
In some ways it is, and in others it's not. It would be basically the same if the corner/box filter was using K1 the same way I am here. If they are using a static filter media then this is a lot different in the principles behind how it works.
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