Yeah, I agree with spongebob - do not put two filters in each side. Instead place a media bag full of carbon in the spot where the second filter bag should go and buy a second HOB filter if you want more filtration. That is what I do and it works like a charm. I also second the API test kit. The strips suck - stick to the liquid test kits.
It sounds like you are heading in the right direction. I am not sure why it is taking your tank so long to cycle, but I do have one thought. If you let the ammonia spike too high in the beginning, your nitrite spike can remain high for a very long time. This is a common problem with fishless cycling. People think that adding a lot of ammonia will be better for the cycle, but it actually ends up extending it. I am not sure what the stocking plan was for the fish you have in there, but if your ammonia had a really high spike, it can severely delay the cycling process. However, this doesn't help you now as the ammonia spike is over - I am just telling you for future references to keep an eye on how high you let the ammonia get when you start up a new tank. I do enough water changes to keep the ammonia and nitrite spike below or right at 1 ppm at all times during the cycle.
Good luck as you progress. I am much happier with your more current nitrate readings. I have no idea why your kit said 40 ppm is safe. Keep it below 20 ppm and preferably below 10 ppm if you can.
Your biowheel is a hob filter as it hangs on the back of your tank... and it moves more gallons per hour since it will suck in additional water from your water column, rather than just filter more of the "same" water that a single filter with two cartridges would. An additional filter will also allow more water to pass through a biological filteration, so this will keep your water quality much cleaner, if you just kept two cartridges in the same filter, it will increase the mechanical filteration by adding another layer for the water to pass through, but won't add much more biological filteration (since you need to replace the pads, this isnt the ideal place for bio to grow, but helps slightly).
I'm always one to over filter and have multiple filters on all my tanks. Why would you use only one pad when you could use two though? The more surface area the water goes over or through is more important than how much water is being pumped through a filter as I understand. This is why an extra cylindrical sponge filter stuck on the end of the existing filter intake adds to the tanks ability to cycle. It gives you more places for the bacteria to colonise thus giving you more capacity to convert ammonia to nitrates, nitrites to nitrates. Wouldn't that be right?
I was editing as you were writing SB. The water as it goes through one filter pad may have most of the particulates taken out making two pads redundant for this purpose, but as far as ammonia and nitrites the water is only partly cycled each time it passes through a pad, which means that two pads only doubles the cycling potential. Where if not on the pads and bio-wheel do the bacteria live then? Most filters don't have bio-wheels and the bacteria have only all the surfaces to live on, and these fiberous pads provide more surface area than the insides of the HOB
Peter, you're right.... but i think when people toss out these pads, they lose that extra surface for bio activity.... a second filter will have a permanent area for beneficial activity (such as the biowheel, or a permanent sponge that u don't remove). A second filter pad in there wont hurt ofcourse, it will only be good as you suggest. But if its choosing between a second filter or a second cartridge, the second filter moves more water and has a bio surface that wont be removed.
Zambize, just so you know, Peter (and Miami) was a major reason i even added a second filter, so we're just getting into the nuances at this point... any additional filteration is a good thing basically.
It does take some time for new bacteria to grow and it's assumed in my understanding that the older pad and the bacteria in the tank will seed the newer pad relatively quickly. I agree an extra filter is great, but filling both filters with as much surface area containing material should be best I think.
I see your point, Peter and I certainly cannot argue with the reasoning, but I have personally never seen that much of a difference in my water quality when using 1 versus 2 pads in these dual pad setups. I used to use 2 pads, but then decided to put media bags full of carbon in there. It seems to me (and again this is only my experience) that this gives me a clearer aquarium than the 2 pad approach. I do not think you will have a problem with the bacteria not having enough surface to grow on if you have 1 pad per channel and a biowheel, not to mention the substrate and any decor you have. Generating large enough bacterial colonies has never been a problem for me (I can't use my cichlid tank as an example as they have over 100 lbs of rock to colonize on :) ). I am upgrading to a canister filter (XP3) here soon anyways, so soon I will not have the choice of multple pads. Ah well.
I wonder if the bacteria can colonise on charcoal? I have nets of old charcoal in my back room tanks that's probably spent, but I leave it in so there's more stuff for bacteria to colonise on. The water in these 2 tanks is fine and I don't have but 2 fish in the big one and hardly feed them. I also just leave the old charcoal cylindrical bits in my canister filters with my planted tanks. I heard that plants need some of the substances charcoal takes out so I haven't changed it in a while in my nicer bedroom planted tanks.
Seems like it's just about perfect. Maybe do water changes half as much now and after a few days or a week get back to us. I think eventually you should get zero ammonia and nitrites with water changes every 2 weeks of 30% of the water each time, and then these changes should be just to lower nitrates. Anybody jump in if there's any other ideas! Good goin. Peter
Yes i think the levels are considerably better than before. Peter hit all the points. And don't make the mistake I just made of adding too many fish at once, even small fish. I added 6 really small rasboras at once, but since my tank is small (20 gallon), it kicked up a mini cycle. But good job, keep it up!
Thank you all for such prompt replies. My next move is to begin adding 6 Black Neon Tetras. My plan is wait until all levels are 0, or extremely close, and then add 3 of the little beauties. Then wait a couple of weeks and if the water quality has remained good, add the remaining 3.
I'd like to add the fish even slower, like 2, 2, and 2, but I'm concerned that they are a schooling fish and they'll already be stressed enough being at only 3 for a while. Thoughts?
