75 Gallon Tank Cycling Tank: ammonia levels constantly high for months

Hello everyone,

I've been lurking around the forum and trying to read and find out as much as possible, but I've reached the point where I feel like I've tried everything and I'm at my wit's end, so thought I'd ask for help.

I currently have a 75 gallon tank with 2 terrapins in it (I am getting a larger one, but it'll take some time). I bought a new Fluval FX6 in mid-May to replace my much smaller and struggling Eheim, which stopped working just after I installed the FX6, which was a bummer as I thought I could run both alongside to ease the whole process a bit. I put in the relevant biomedia (bio-rings etc) transferred some of the established media from the old filter to help the FX6 cycle more quickly, and set it up knowing that it would likely take much longer given the size of the filter relative to the tank and the fact that I was doing a 'turtle-in' cycle with a heavier bioload.

However, it's now been over 3 months, and it just doesn't seem to be cycling or the cycle is stalled. Initially, I was using amquel+ as the ammonia levels rose, but I stopped in June as soon as I read that this may affect the cycle, and kept dosing with prime with every water change. I've stopped using stability also, and dumped a bottle of Dr Tims' Nite-Out in July to see if it helped. However, my ammonia levels have constantly been rising with no corresponding sudden increases in nitrite or nitrate until August. I've been doing 25-30% water changes every few days to keep ammonia low at 1-2ppm.

The problem is, if I do a major water change (50-80%) the ammonia levels decrease, but the nitrite spikes, as does the nitrate. However, after a few days, nitrite and nitrate disappear, whereas just ammonia keeps rising. I've only done a major change 3 times when ammonia reached over 4ppmish, and I haven't touched the filter except at the beginning of August, when I did check it and just rinsed it in aquarium water without actually cleaning/or squeezing the media at all (turtles are dirty!)

After rinsing the filter, doing the water change and cleaning stones inside the tank (I have no substrate), I suddenly saw a major spike in nitrites and nitrates, which reached 2-3ppm and 40-80ppm respectively. Ammonia was dropping from 0.5 to 0.25-0. Hallelujah! Tank cycling? But after a week and a half and a few water changes to keep levels in control, ammonia is rising and nitrite and nitrates are dropping again, from 2 to 1ppm and 40 to 20ppm.

What could be causing this issue? Is it just that the ammonia converting bacteria hasn't established or there isn't enough of it? Have I done something to stall the cycle, like the major water changes? It seems like there is some nitrite and nitrate converting bacteria, right from June.

Could it be my pH? The water in my area is very soft and below 6.8. pH adjusters don't really do much and are expensive, but maybe ammonia is just converting to ammonium and registering on my test, thus no bacteria converting to nitrite? Temperatures are pretty constant at 24-27 C, 75 F. I use API's freshwater test kit, bought a new one, and my tap water all tests at 0.

I'm tearing my hair out as my line of work means I don't have the time to keep going like this for much longer. Luckily, turtles are hardier than fish, but one of them is injured and so I'm being as careful as I can.

Does anyone have any advice? I would really appreciate any insight. I'm sorry for the long post!

 

Yeah your pH could be too low. Water changes won't stall your cycle so dont worry about that. Maybe try some crushed coral in the filter to raise your pH naturally and stabilize it.

 

Welcome to Fishlore

I agree with StarGirl If you can get your pH stabilized up to at least 7 this cycle should finish up. Crushed coral or even oyster shells should help you accomplish it. I do have to wonder how your turtles shells are doing with this soft water. Are you adding extra calcium for them?

You may want to consider getting some turtle calcium such as this one Amazon.com : Zoo Med 10 Pack of Dr.Turtle Slow-Release Calcium Block : Pet Supplies

I don't have turtles but use if for my snails shells. I have to think adding the extra calcium will also help stabilize the pH in your very soft water.

 

In addition to what’s already been recommended, what are you feeding your turtles? Any chance you have old/rotting food that keeps accruing in the tank, if the turtles aren’t eating it all fast enough? That could be heightening the ammonia problem, in addition to the potential pH issue.

 

Welcome to Fishlore

I agree with StarGirl If you can get your pH stabilized up to at least 7 this cycle should finish up. Crushed coral or even oyster shells should help you accomplish it. I do have to wonder how your turtles shells are doing with this soft water. Are you adding extra calcium for them?

You may want to consider getting some turtle calcium such as this one Amazon.com : Zoo Med 10 Pack of Dr.Turtle Slow-Release Calcium Block : Pet Supplies

I don't have turtles but use if for my snails shells. I have to think adding the extra calcium will also help stabilize the pH in your very soft water.

Thank you to both of you! I will see if I can get crushed coral and add to my filter - is there any particular place I should put in my canister?

I've been giving them calcium drops when I feed them and use calcium blocks in my water like you do for your snails: their shells are doing okay for now - the vet informed me my younger one was slightly low on her calcium levels as she was gravid for too long and refused to nest where we made a spot. She'd injured her leg during a dramatic escape attempt, right from the tank and down my stairs. Worrying but spectacular!

In addition to what’s already been recommended, what are you feeding your turtles? Any chance you have old/rotting food that keeps accruing in the tank, if the turtles aren’t eating it all fast enough? That could be heightening the ammonia problem, in addition to the potential pH issue.

I feed them a standard food mix (King British ) every few days - they're still young and they refuse veggies, so it's not as messy. I've been making sure I clean the debris once they've finished eating and I check regularly beneath stones, but will try and reduce feeding amount and maybe that will help? The filter is pretty powerful so I was hoping it wouldn't be such a major problem, but turtles produce a lot of ammonia I guess. Thank you for the advice.

 

Thank you to both of you! I will see if I can get crushed coral and add to my filter - is there any particular place I should put in my canister?

I've been giving them calcium drops when I feed them and use calcium blocks in my water like you do for your snails: their shells are doing okay for now - the vet informed me my younger one was slightly low on her calcium levels as she was gravid for too long and refused to nest where we made a spot. She'd injured her leg during a dramatic escape attempt, right from the tank and down my stairs. Worrying but spectacular!


I feed them a standard food mix (King British ) every few days - they're still young and they refuse veggies, so it's not as messy. I've been making sure I clean the debris once they've finished eating and I check regularly beneath stones, but will try and reduce feeding amount and maybe that will help? The filter is pretty powerful so I was hoping it wouldn't be such a major problem, but turtles produce a lot of ammonia I guess. Thank you for the advice.

It should work well wherever it is in the filter. I have the think the best place for it will be situated where it is the last thing the water goes through. By doing so it isn't going to get a buildup of mulm and should dissolve better if kept cleaner. Be sure to rinse it off before putting it in your filter. If this step isn't taken the pH will spike too quickly. Once rinsed and put in the filter it will take several days for it to raise the pH up as high as it is going to. I would start out with about a cup of it for this size tank.

I will recommend you get the ammonia down as low as possible before adding the crushed coral. As the pH climbs the ammonia will get more toxic so we need to balance things out. Hopefully by getting the pH up and stabilized this cycle will finally finish up.

Oh my, what an adventure this little lady went on. Hopefully her wounded leg will heal quickly and you have found a way to prevent another escape.

 

Good move stopping the use of Amquel+. If you have water with a low KH/GH long term use of Amquel+ can cause a pH crash. Me and a tankful of fish learned this the hard way.

 

It should work well wherever it is in the filter. I have the think the best place for it will be situated where it is the last thing the water goes through. By doing so it isn't going to get a buildup of mulm and should dissolve better if kept cleaner. Be sure to rinse it off before putting it in your filter. If this step isn't taken the pH will spike too quickly. Once rinsed and put in the filter it will take several days for it to raise the pH up as high as it is going to. I would start out with about a cup of it for this size tank.

I will recommend you get the ammonia down as low as possible before adding the crushed coral. As the pH climbs the ammonia will get more toxic so we need to balance things out. Hopefully by getting the pH up and stabilized this cycle will finally finish up.

Oh my, what an adventure this little lady went on. Hopefully her wounded leg will heal quickly and you have found a way to prevent another escape.

I've ordered some today and will make sure I rinse and do a big water change to get the ammonia down before putting it in once it arrives. Hopefully the pH will at least hit 6.8-7 and it'll finally get this cycle finished.

All calm at the moment - she's got a grill above her so she can't try her luck any time soon. Thanks again for your help

Good move stopping the use of Amquel+. If you have water with a low KH/GH long term use of Amquel+ can cause a pH crash. Me and a tankful of fish learned this the hard way.

Yeah, I read that it affects pH and that it inhibits the cycle. It kept giving me odd readings when I tested the water hours later (ammonia from 0.5 previously to 0), so I did some research and stopped ASAP and just stuck to Prime. Sorry to hear about your fish!