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Re-cycling a tank


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Hello, I recently destroyed my cycled tank, I have a 210g with about 50 adult cichlids. I was wondering how I should properly go about restarting the tank.

I have 2 canister filters at 500+ gph, i clean out the filter once every month or two, it has 4 layers and i cleaned out the top one of gunk by rinsing it in the dirty tank water like i've seen on youtube etc. Last month I got a fish smell and decided its been a year or a bit longer since I have 2 filters how about i restart one to help clear up the green tint water. That didn't work so I did the 2nd filter a little over a month later so that I would still have good bacteria to tackle stuff on the tank. Well that crashed the system I now have a horrible toxic smell that's filling my house. I've had the top off with a fan out the window to help with this. Yesterday morning I had enough of the smell and did a 70% water change. (always been scared of big water changes) This didn't help my parameters much. I use the API master test kit, I followed the instructions to the letter, Yesterday I was at 4.0 ppm ammonia, .25 nitrite, 160 ppm nitrate. After the 70% water change I waited till this morning so roughly 20 hours or so. 1.0 ppm ammonia, 2.0 ppm nitrite, a bit darker than 80 ppm nitrate but less dark than the 160 i'd guess somewhere on the side leaning closer to 80ppm.
The fish look healthy, they are eating as always, not gasping, water looks crystal clear, smell is down but still potent, maybe fills the room instead of house.

What should I do, should id do big water changes daily? should I wait for the bacteria to grow and take hold of everything and just deal with the smell and vent it out the window to the best of my ability? Should I keep adding beneficial bacteria?

Just to also add, I put prime in the water then added to the tank then put in 200g worth of quick start beneficial bacteria in a hour later not sure if those counter each other. There's 0 extra food ever, and their waste is relatively small.

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 I'd be curious to hear a suggestion for this. I am having a similar situation with a goldfish tank. I have been doing weekly water changes. Today I got some nitrifying bacteria that I will be dumping in my tank to see if it will help to seed my bio-filter. My plan is to add it every day for a few days or until I run out.

I did this once before with the same fish when I first started (I learned to not by on impulse the hard way) and I think it worked... when I tested after treating the water for a few days I noticed that the ammonia was lower. I then tested the nitrites and nitrates and noticed that the nitrites were high so I knew the process was working. The only thing I don't know is if the change from ammonia to nitrites was from the bacteria or was already in process and I just hadn't been testing it.

I am currently feeding protein every other day to lower waste.

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So at this point in time you are doing a fish in cycle. The numbers are reading high because whatever a fish eats, comes out as waste. 50 cichlids is a lot, so its a lot of waste.

I'd try to keep those numbers lower while you rebuild the BB as otherwise you're likely to give the fish ammonia burns or worse with numbers staying that high.  So test the water every other day or so for the next month or however long it takes that cycle to get going and caught up. Do water changes every other day to keep the levels more reasonable. Try and keep ammonia and nitrite as low as you can. Does daily with prime to keep the ammonia neutralized so long as you are reading any number higher than .5 on the ammonia test - this is to help prevent ammonia burns on the fish. Its not fool proof long term, but hopefully this won't take long.

I say hopefully, because your tests show you have nitrates in the water - this means there's got to be some BB left. Just probably not enough to handle the full load of all the cichlids. So, until the BB builds back up to sufficient numbers, you'll  also have ammonia and nitrates - so you have to do water changes to combat those. With any luck, your continued testing will show the nitrates remaining higher (relatively.  Ideally a good cycled tank is usually considered to keep the nitrates under 40ppm) while ammonia and nitrite drops off as you continue to do water changes. If the nitrates are still above 40ppm, its time to do another water change to help bring those numbers down. 

Keep an eye on your fish. If you notice lots of rapid breathing, or holding gills open with lots of redness in the gills, this is likely ammonia burns, so a water change needs to happen to bring it back down to levels they don't find as stressful. 

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