Urgent Help With Sick Cory

Hi, I’m having some serious problems with my JuliI cories and I need some help to try and save them as I don’t know what’s gone wrong.

Tank
80 litre tank running since April with an Oase Bioplus thermo 200 filter/heater and an air stone. Tank temperature sits at 24C.
Stocked with 8 glow light danios, 3 peppered Corys and 4 JuliI Corys.


Maintenance
Weekly water changes of 30% and water treated with dechlorinator before adding to tank. Different sections of gravel vacuumed every week (front one week, back the next).

Parameters
Tank has been cycled and running well since April. API test strips used weekly for ph, nitrite, nitrate, carbonate and general hardness and a separate test tube dropper kit used to test ammonia weekly.
Readings this morning:
Ammonia: 0
Nitrite: 0
Nitrate: 30
pH: 7.5

Feeding
Flake every day for the danios and alternate shrimp and algae pellets used for the Corys.

Illness & Symptoms
I’ve had 3 of the JuliI Corys for 4 weeks now and the 4th since first stocking my tank in May. I’ve had the peppered Corys for 5 weeks. I did have 4 but one died yesterday.

Yesterday I noticed one of my peppered Corys floating on the surface of the water. There were no signs of disease and he was happily feeding the night before so I’m not sure why he died. I then noticed one of the JuliI Corys darting to the top of the tank, breathing heavily and acting like he was fitting, gulping at the surface then sinking to the bottom of the tank and flashing the gravel. I tested the water and everything was fine (see above) but I decided to do a 30% water change in case there was something I was missing. He was still acting erratically darting to the surface then floating to the ground with rapid breathing and I didn’t think he would survive the night.

Today we still have the occasional darting to the surface and fast breathing and I now have another JuliI behaving in the same way but more severe. I again tested the water and it was the same. I’ve done another 30% water change as I’m not sure what else to do? I have noticed some red markings on the bottom fins of the 2nd JuliI where they join its body that I hadn’t seen before.
The peppered Corys and danios are absolutely fine it’s just the Juliis that seem to be struggling.

Any ideas of what the problem could be? I have some melafix handy if that would help? As of last night they were all eating well so this has happened very quickly.

Thank you

 

The behavior that you described (darting, flashing, gasping, trying to escape the water) are symptoms of poisoning. Water test strips are often inaccurate, but the numbers you have suggest your nitrates are high, meaning nitrate poisoning is a possible culprit. It’s also possible you had an ammonia spike at some point that went unnoticed. If you can switch to the API freshwater master test kit. As for now keep doing water changes, vacuum your substrate (sometimes pockets of anearobic bacteria or detritus become trapped in substrate and when released cause parameter spikes) rinse your filter media in tank water (excess detritus collects on filter media and if released back into tank can cause nitrate spikes) and look into the possibility that you are overfeeding or that a plant is rotting in your tank. Also remove the dead bodies because they will cause ammonia spikes. As for the Melafix scaleless fish may be sensitive to it and it is quite useless. It’s only use is to help fish who are injured heal, but most fish can heal on their own and meds will just stress them out

 

Thank you so much for your help. I cleaned out the filter as well as doing another couple of water changes over the last few days and that seems to have done the trick. I’ve now ordered the master kit to get more accurate readings too. The Juliis are back to swimming normally but will this have had a lasting effect on them in any way? I tested my tap water also and the nitrate reading was 40. Is there anything I can do or that you would recommend to try and lower this before doing a water change? The tank is moderately planted.
Thanks

 

Thank you so much for your help. I cleaned out the filter as well as doing another couple of water changes over the last few days and that seems to have done the trick. I’ve now ordered the master kit to get more accurate readings too. The Juliis are back to swimming normally but will this have had a lasting effect on them in any way? I tested my tap water also and the nitrate reading was 40. Is there anything I can do or that you would recommend to try and lower this before doing a water change? The tank is moderately planted.
Thanks

If you can test your tap water. Sometimes it can have high nitrate

 

If you can test your tap water. Sometimes it can have high nitrate

Yes, I have 20ppm nitrates out of the faucet, which is useful to know so that I can guage what's a normal and abnormal nitrate reading for my tanks. If it's less than that, I know that plants are using it; if it's more than that (which it never is), I know that I have an excess of nitrates (and thus nitrites and ammonia production) for my setups, for example.
40 nitrate is probably the max for most fish before starting to get to the danger zone. This is where knowing what your tap nitrate level comes in handy, so you know what your starting point is and anything above that is coming from the aquarium.

 

Yes, I have 20ppm nitrates out of the faucet, which is useful to know so that I can guage what's a normal and abnormal nitrate reading for my tanks. If it's less than that, I know that plants are using it; if it's more than that (which it never is), I know that I have an excess of nitrates (and thus nitrites and ammonia production) for my setups, for example.
40 nitrate is probably the max for most fish before starting to get to the danger zone. This is where knowing what your tap nitrate level comes in handy, so you know what your starting point is and anything above that is coming from the aquarium.

Many would say 20 is the limit. You can mix RO or spring water with their tap water

 

Many would say 20 is the limit. You can mix RO or spring water with their tap water

40 is fine, I rarely hear 20.

 

Many would say 20 is the limit.

And I'd probably agree. I think some fish can handle higher nitrate than others, though/some fish have lower tolerance of nitrate levels. I'll add that it probably depends on how fast the nitrates are being used by plants or even how often one water changes. I've heard of some people dosing fertilizer to very high nitrate levels to keep up with the plants they keep. But for the average person, that's not the case.

 

On some test kits I’ve seen 20 was marked as unsafe, and some people on other posts have said 20, but others say 40. If the tank itself has healthy conditions I feel like 40 would be fine