Can't beat old tank syndrome

So I was asked my one of my mums friends to help her find out why the new fish she was buying kept dying within a day or two. I went to her house and tested the water and it instantly sent the api nitrate test dark red, so over 160ppm, I retested with a nt labs test and the same result. Turns out she hadn't done a water change or gravel clean since she set the tank up 7-8 months ago.
I have since cleaned the filter out, which was in awful condition, the bottom of the filter was nearly 1 1/2 inches thick and everything inside was covered in fish waste and sludge. Made me feel abit ill. I have also gravel cleaned multiple times because the water was nearly black after the first few goes and under the decorations was thick with waste.
I have given the tank a 50% water change and daily 25% water changes for the last week, so 8 water changes in total, and the nitrate is still reading at over 160 ppm on the api test. I have ordered some jbl nitratex for her as a next step but I don't know what will be causing it to be so high still, I have searched for dead fish and anything rotting. I have suggested she go to a fish shop and buy some live plants as an extra step but I don't think a few plants will fix this. I have also taken over feeding the tank until it is sorted to make sure she isn't overfeeding it while I'm away. She only lives 5 minutes from me so not really an issue.
Does anyone have any suggestions on what else I could try to get the tank under control, I have got everything else under control but can't get nitrate.

 

Does she have Nitrate in the tap water? I would say just keep doing water changes until it goes down.

 

Have you tested her water source? Maybe her tap water has nitrates or ammonia in it

 

What's the nitrite reading? Careful that the nitrite reading is not overmagnifying the nitrate reading.

 

Does she have Nitrate in the tap water? I would say just keep doing water changes until it goes down.

Thanks all. I did test her tap water and it has 15ppm nitrate in it so I know it will be slowing down the drop but I cant even get it below 160ppm yet

What's the nitrite reading? Careful that the nitrite reading is not overmagnifying the nitrate reading.

Nitrite and ammonia are both undetectable now, was a slight rise in nitrite 0.25 when I started moving everything but that has now gone back to undetectable after 12 hours

 

Nitrite and ammonia are both undetectable now, was a slight rise in nitrite 0.25 when I started moving everything but that has now gone back to undetectable after 12 hours

Gotcha. Any reason why you did not just do a 100% water change? Are there still fish in there?

 

Gotcha. Any reason why you did not just do a 100% water change? Are there still fish in there?

She has six mollys in there at the minute that have been In there since the start so are use to the high nitrate. Was thinking about doing a 100% water change if I couldn't get it under control any other way but I also didn't want to shock the fish with sudden clean water

 

She has six mollys in there at the minute that have been In there since the start so are use to the high nitrate. Was thinking about doing a 100% water change if I couldn't get it under control any other way but I also didn't want to shock the fish with sudden clean water

That's fair.

Though surprising all those water changes has not reduced nitrate below 160ppm though. There should only be like 6.7% original water left, so yeah.

Anyways, I suppose it's just about keep on doing water changes until nitrate is within sensible levels, yeah.

 

She has six mollys in there at the minute that have been In there since the start so are use to the high nitrate. Was thinking about doing a 100% water change if I couldn't get it under control any other way but I also didn't want to shock the fish with sudden clean water

Your point about sudden clean water is an important one. . .

So long as the fish aren’t currently in distress, I’d be careful not to change too much too soon. Probably 50% every day or even every other day.

 

Your point about sudden clean water is an important one. . .

So long as the fish aren’t currently in distress, I’d be careful not to change too much too soon. Probably 50% every day or even every other day.

The fish don't seem stressed at the minute. They are still eating happily when they are fed and don't seem to be loosing condition.
I did the large one at the start and then smaller ones daily so they had some time to get use to the water changing but it doesn't seem to be helping. Just looking for anything I might have missed

 

The fish don't seem stressed at the minute. They are still eating happily when they are fed and don't seem to be loosing condition.
I did the large one at the start and then smaller ones daily so they had some time to get use to the water changing but it doesn't seem to be helping. Just looking for anything I might have missed

You’re sure you’re doing the nitrate test exactly according to the instructions?

If so, the only thing I can think is that the nitrate level was incredibly high before you started the water changes. Which could be a possibility given the lack of water changes previously and the condition of the filter?

 

You’re sure you’re doing the nitrate test exactly according to the instructions?

If so, the only thing I can think is that the nitrate level was incredibly high before you started the water changes. Which could be a possibility given the lack of water changes previously and the condition of the filter?

Yeah I've been doing the test correctly. Tested my own tank to make sure the tests are working and they have come back as expected. I think I'll keep doing water changes for abit longer and add the nitratex when it arrives before testing something more extreme like large water changes

 

Yeah I've been doing the test correctly. Tested my own tank to make sure the tests are working and they have come back as expected. I think I'll keep doing water changes for abit longer and add the nitratex when it arrives before testing something more extreme like large water changes

Keep us posted.

 

7-8 months is about 28-32 weeks. lets say her fish produce 10ppm nitrate per week. that's about 280-320ppm. a 50% would bring it down to around 150ppm. factor in the 15ppm from the tap. 165ppm nitrate.

the first 25% daily water change will take away about 1ppm from the weekly nitrate, and about 37ppm from the 165ppm. so you should have about 124ppm + 15ppm = 139ppm nitrate.

the second 25% will take away 1ppm from the weekly, and about 35ppm from the 139pm. now its 103+15= 118ppm.

just estimating now, after the 7th 25% water change it should be down to about 40-50 ppm nitrate.

did you do any gravel vac?

you said there are six mollies. what size is the tank?

agree with the small water changes so the mollies can acclimate to the lower nitrate.

 

7-8 months is about 28-32 weeks. lets say her fish produce 10ppm nitrate per week. that's about 280-320ppm. a 50% would bring it down to around 150ppm. factor in the 15ppm from the tap. 165ppm nitrate.

the first 25% daily water change will take away about 1ppm from the weekly nitrate, and about 37ppm from the 165ppm. so you should have about 124ppm + 15ppm = 139ppm nitrate.

the second 25% will take away 1ppm from the weekly, and about 35ppm from the 139pm. now its 103+15= 118ppm.

just estimating now, after the 7th 25% water change it should be down to about 40-50 ppm nitrate.

did you do any gravel vac?

you said there are six mollies. what size is the tank?

agree with the small water changes so the mollies can acclimate to the lower nitrate.

Well that's better maths than I could do. Yeah I gravel vac with every water change I'm doing.
The tank is a fluval roma 125 with a fluval 207 for filtration. Apparently bought it second hand so didn't come with the original internal filter

 

since you cleaned out the canister filter and gravel vac, i would suggest upping the water changes to 50%. test the tank water before each water change. once you get it down below 40ppm, you can stop the daily water changes. and a 50% weekly water change should be able to maintain it.

 

Well that's better maths than I could do. Yeah I gravel vac with every water change I'm doing.
The tank is a fluval roma 125 with a fluval 207 for filtration. Apparently bought it second hand so didn't come with the original internal filter

jtjgg theory and math make a lot of sense, but I’m not sure we know enough about the history/stocking of the tank beyond what’s currently in it.

I don’t disagree that it seems that the amount of water you’ve changed should’ve made more of a difference, but it apparently hasn’t. So, my advice is the same. . . Stick with the larger water changes every day or couple days.

Good luck and keep us posted.

 

One more thing that might help is reducing or even completly removong the gravel. Then the next day, dump the filters that will be full of all the crud that comes up. Clean the gravel and decide if you want to put it back. the less gravel, the less trapped waste in the future.

 

One more thing that might help is reducing or even completly removong the gravel. Then the next day, dump the filters that will be full of all the crud that comes up. Clean the gravel and decide if you want to put it back. the less gravel, the less trapped waste in the future.

Thanks. I hadn't thought about just removing the gravel. Will give that a try soon if a few more water changes doesn't help. I've just had to clean the filter again because it was full again. I thi k where I've been moving everything it's all been stuck in the filter again

 

A prefilter might be easier to clean in your case. you can removing and clean it instead of the entire filter. You can put a plastic bag over it to catch the crud, remove it, rinse it, return it.

 

When you have extremely high nitrate the best solution is very large water changes [75-100%]. I think some kits only read to a certain amount and you might be way over 160ppm. Its a math issue if you have 100ppm and you change 50% of the water you should drop to 50ppm. Another 50% water change will only bring it down to 25%. It takes a long time to get to accepted levels. I'm not sure if its a shock to fish to go from a high nitrate to low. I would do a large % of the water[ 75% or over] and see if it comes down.

 

I'm not sure if its a shock to fish to go from a high nitrate to low.

Yes, it definitely can be. That’s why I suggested in a post above to bring the nitrate level down over a period of days, not all at once.

 

Thanks for all of the help everyone. I've mentioned a pre filter to her but it's up to her if she spends money on it.
I have now managed to get a reading slightly below the 160ppm, still nowhere near sorted yet, but hopefully on the right track. It has taken one 25% and three 50% water changes since I first posted this to get the slightly below 160 so I dread to think how high the nitrate actually was.
Hoping it on the home straight now to being fixed. Thanks for the help

 

After you rescue this tank, is she willing to do the required weekly maintenance? A prefilter will not compensate for lack of maintenance as I'm sure you know.

 

After you rescue this tank, is she willing to do the required weekly maintenance? A prefilter will not compensate for lack of maintenance as I'm sure you know.

She says she is willing to do the work and I can only take her word for it. She now knows what she's done wrong and how to maintain a tank now. she also knows that I wouldn't be willing to do it again so she has no choice. I did offer to take the fish off her hands if she didn't want the tank anymore but she was adamant she will look after it now. Nothing more I can really do

 

Thanks for all of the help everyone. I've mentioned a pre filter to her but it's up to her if she spends money on it.
I have now managed to get a reading slightly below the 160ppm, still nowhere near sorted yet, but hopefully on the right track. It has taken one 25% and three 50% water changes since I first posted this to get the slightly below 160 so I dread to think how high the nitrate actually was.
Hoping it on the home straight now to being fixed. Thanks for the help

Based on the math your tank would have started at 3000 ppm or so, not sure how that's possible to be perfectly honest. The bucket of old water, leaves, and dead squirrels I found outside the other day wouldn't have 3000 ppm of nitrates (found on an old property, not the point lol)

 

Based on the math your tank would have started at 3000 ppm or so, not sure how that's possible to be perfectly honest. The bucket of old water, leaves, and dead squirrels I found outside the other day wouldn't have 3000 ppm of nitrates (found on an old property, not the point lol)

Hahaha that's rediculous. Surely nothing could survive in that. Oh well they are getting better now and hopefully they will never have to have it again

 

If you could let some hornwort or moss slip in the tank it could help.