Lost my pygmy corydoras after a water change

[Gill]

Yeah water shock does not sound to be the problem. As big cold water changes creates spawning behaviour in corydoras species of all kinds. As in the wild when it rains and they get a huge change in temp rapidly.

 

[Calamardo Tentaculos]

Could be Oxygen depletion.
How much water did you change?
What time of day did you do it?
How much Seachem Prime did you dose into the RO/Tapwater?

50% water change in the morning. 1.5ml for 10l.

If it helps I suspect the cooler 50% water change and subsequent fish loss are unrelated in the grand scheme of things. So don't beat yourself up about it.

Looking back at some of your other posts it appears you've already lost a number of pygmy corydoras over the last month or so, certainly before this water change?

Not saying this to be a smart ars#, but suspect either the tank or fish themselves have some underlying issue that's causing the loss, although admittedly I don't know what this could be.

I know and I have been trying to figure out what is the issue with my tank. Perhaps I may have to reset my tank entirely after the Christmas holidays. Something is certainly wrong with this tank.

That doesn't sound like cold shock to me, the prime symptom I've seen in cold shock is lethargy. My instinct would be either toxin in the added water or toxin in the tank water made more toxic by the water change.

BRJP1 has given the exact advice I would. Test everything to see if there's a hidden problem.

Water tests done showed no ammonia or nitrite spike. I am wondering whether my test kit is faulty. Same water used on my neocaridina tank has no issues whatsoever.

@I am Ken - I think there are some good plausible causes here, but it's hard to nail at the moment. As others have mentioned, a 50% water change should not be a problem if all parameters are correct during that change.

As we can't isolate the problem for sure, I can only suggest stepping back and doing some checks at this stage.

• Test the water for basics to understand where you are right now (Ammonia, Nitrite, Nitrate, Chlorine, TDS, Temp ) and record that somewhere.
  • I would also test both your raw tap water and RO water for Ammonia, Nitrite, Nitrate, Chlorine and TDS to understand the readings at the source.
• It looks like you have a sponge filter and assume that is working? Keep that running, and only clean it when it's clogged to let any bacteria build up. (i.e. let's not remove any goodness by over-cleaning).
  • I can't tell if it's the camera image due to light, but there is a certain amount of milky haze in the water - is that the camera light or is it crystal clear in reality?
• Check/increase the aeration by upping surface agitation or enough air bubbles to create that agitation.
• Stick your finger (gently to not disturb too much but enough to 'coat' your finger) into the gravel and give it a sniff test to check that it does not smell eggy or sewage-like.

I know none of this is an answer, and it could be a temperature issue caused by the change, but I would just take stock of the environment right now and check if anything comes to light.

I have tested both my tap and RO water in the past and am familiar with the parametres. TDS about 300-350 ish for tap water and 15 for RO water.
Yes, water was slightly milky.


The remaining pygmies were doing well for a week or two before this. I had started feeding them micro worms that @dw1305 provided and everything seemed fine. I then cleaned my HOB filter and did a water change, and this happened. I am wondering about ammonia in the gravel since I used the gravel vacuum to clean it, but that should improve the water quality not worsen it.

 

[Bradders]

Yes, water was slightly milky.

Interesting.
So, you may have a lot of bacteria in the water column. i.e. enough bacteria build up in the water column that you can see it. The Ammonia to Nitrate cycle is much easier to achieve than crystal-clear water.

To round this off:

1. How often do you clean your Sponge Filter?
2. How do you clean your Sponge Filter? (i.e. under tap water, in tank water).

 

[Bradders]

I then cleaned my HOB filter and did a water change, and this happened. I am wondering about ammonia in the gravel since I used the gravel vacuum to clean it, but that should improve the water quality not worsen it.

And this.

Is it possible you did a water change, cleaned the Sponge Filters, cleaned the HOB Filter and the Gravel in short timescales?

 

[Calamardo Tentaculos]

Interesting.
So, you may have a lot of bacteria in the water column. i.e. enough bacteria build up in the water column that you can see it. The Ammonia to Nitrate cycle is much easier to achieve than crystal-clear water.

To round this off:

1. How often do you clean your Sponge Filter?
2. How do you clean your Sponge Filter? (i.e. under tap water, in tank water).

Used tank water.

And this.

Is it possible you did a water change, cleaned the Sponge Filters, cleaned the HOB Filter and the Gravel in short timescales?

Yes, I actually just added activated carbon to my hob filter a few days ago.

 

[G H Nelson]

Could be Oxygen depletion.
How much water did you change?
What time of day did you do it?
How much Seachem Prime did you dose into the RO/Tapwater?

50% water change in the morning. 1.5ml for 10l.

Seachem Prime should be dosed at 1.25ml per 50 Litres......if you did a 50% water change that water being 50% RO.
That would mean you have added 5 litres of Tap water dosing 1.5ml Seachem Prime.
That could possibly be the answer.....doing the water change in the morning when the aquarium would be low in Oxygen is part of the puzzle.

The Prime dosage could have done unrepairable damage and distressed the Corys resulting in their demise.

 

[_Maq_]

I am wondering about ammonia in the gravel since I used the gravel vacuum to clean it, but that should improve the water quality not worsen it.

Wrong! Very wrong you are. Vacuuming is dangerous because you release whatever is buried in the sediment.
The sediment is not oxygenated and its redox is negative. If you disturb it, unexpected actions and re-actions occur.

 

[G H Nelson]

Warning this video is not for the squeamish!

You will notice there is very little surface agitation.

seachem prime fish death - Search Videos

www.bing.com

 

[G H Nelson]

Wrong! Very wrong you are. Vacuuming is dangerous because you release whatever is buried in the sediment.
The sediment is not oxygenated and its redox is negative. If you disturb it, unexpected actions and re-actions occur.

That gravel cleaning could be part of the chain of events that resulted in the loses!

 

[Bradders]

50% water change in the morning. 1.5ml for 10l.

Seachem Prime should be dosed at 1.25ml per 50 Litres......if you did a 50% water change, of that water being 50% RO.
That would mean you have added 5 litres of Tap water dosing 1.5ml Seachem Prime.
That could possibly be the answer.....doing the water change in the morning when the aquarium would be low in Oxygen is part of the puzzle.

The Prime dosage could have done unrepairable damage and distressed the Corys resulting in their demise.

Yes, sadly, Prime has the dithionite chemical in it, which I understand can be easier to overdose than other products. i.e. not very forgiving with errors.

 

[Calamardo Tentaculos]

What the hell? So I have to watch out for Prime overdose and avoid vacuuming the gravel as well?

So what do I do now? Do I create a bare bottom tank then or what substrate should I do?

 

[_Maq_]

So what do I do now? Do I create a bare bottom tank then or what substrate should I do?

It's an old common observation that doing all maintenance at once is not recommendable. Both the sediment and filter are environments which mature and develop some kind of equilibrium. If you disturb any of them, stability is lost. It seems, though, that the other part is often capable of saving the day if left undisturbed.
I've cancelled all biological filtration in my tanks. I don't expect you'll follow my example. People are getting good results with mechanical pre-filters. These keep the filter itself free of excess dirt and you can leave it untouched for long time, easily several months. You only regularly clean the pre-filter.
The other thing is vacuuming the gravel. I think there's no universal practice. I do not vacuum at all, and I'm far from the only one. A tank with moderate level of pollution - basically the (fish)food - can handle detritus indefinitely. Snails, protozoa, and bacteria decompose it up to complete mineralization. It takes time, indeed, but in the meantime detritus in the substrate fulfills natural functions. Detritus is not bad per se. It's bad only if your tank is in poor shape and detritus accumulates.
I rely solely on the substrate (sediment) to host microbial community, and I do my best not to disturb those invisible creatures. They are sensitive and seek the right spot to settle and proliferate. You can easily imagine that if you vacuum such a substrate you disturb the microbes and their 'dwellings' substantially. After that, it takes time before they re-settle and resume doing their jobs. These jobs are very variable, and only one of them is the famous nitrification, but they are all very important for well-being of the whole tank.
So I try not to touch the sediment, and if I have to re-plant some plants, I'm wary not to move the sand (gravel, aquasoil) more than necessary - using tweezers and transplanting only when truly needed.

 

[Bradders]

I've cancelled all biological filtration in my tanks. I don't expect you'll follow my example. People are getting good results with mechanical pre-filters. These keep the filter itself free of excess dirt and you can leave it untouched for long time, easily several months. You only regularly clean the pre-filter.

@Calamardo Tentaculos - Although different to Maq, the principle is the same for me. I have a typical canister filter with a pre-filter that I clean weekly. The sponge/HEL-X13 media in the main filter compartment has not been cleaned for six months. I also never clean the gravel.

The good news is that we have honed in on the problem and, therefore, prevent it from happening again. Something in the mix of a) over-cleaning and b) over-dosing has caused a problem. Although we cannot be 100% sure, it does feel like this is the root cause of the unfortunate event.

 

[erwin123]

The situation in this tank is unusual because there are no plants/very few plants in the substrate. An extensive plant root system actually helps to prevent build up of nasty toxins.

I would add, so does regularly vacuuming of the substrate if you do it regularly, how could there be an opportunity for the H2S to build up?) On the other hand, if you do haven't vacuumed the substrate for many months and then decide to do so, there might be danger.

I regularly vacuum the substrate every 3 weeks with no issues to my Corydoras, but I have plants with extensive root systems in the substrate as well.

 

[Bradders]

The situation in this tank is unusual because there are no plants/very few plants in the substrate. An extensive plant root system actually helps to prevent build up of nasty toxins.

I would add, so does regularly vacuuming of the substrate if you do it regularly, how could there be an opportunity for the H2S to build up?) On the other hand, if you do haven't vacuumed the substrate for many months and then decide to do so, there might be danger.

I regularly vacuum the substrate every 3 weeks with no issues to my Corydoras, but I have plants with extensive root systems in the substrate as well.

I think that is an excellent question/point to raise. And I should explain my personal reasons - especially as I have asserted my view on someone else without qualification/detail.

The over arching reason I don’t clean my gravel is because everyone told me I must clean my gravel. 😁 In reality, I was wondering why it needed regular cleaning when it does not happen in nature. Yes, a closed system aquarium is not exactly nature, but we do try to get as close as possible and understand how/why things work.

To cut a (very!) long story short, my research on aquariums and some experimentation led me to believe in a well filtered (including good flow), well oxygenated, carefully stocked, lightly planted and lightly fed aquarium then the chances of the gravel going ‘toxic’ was very unlikely . Adding to the fact that deep cleaning of the gravel is time consuming, a little stressful for my fish and another thing on the maintenance list, I decided to take the risk of leaving that aspect alone.

It’s important to note that I am NOT denying gravel can become ‘toxic’ and that toxicity can be lethal to fish. I just setup my environment to a level where I felt the risk of not cleaning my gravel was very low indeed in comparison to other risks - and where attention should be focused.

Despite my experiments, I do check my gravel at a very basic level. I take small samples out and sniff test it! (Who would have thought I would be doing that in the hobby!). If it does not smell bad then I simply don’t worry about it and think the chances of it being a risk to the inhabitants as extremely low.

As a side note, I am a believer that over-cleaning can cause other issues - especially in the filter media department but also the gravel. So I guess I have a bias to only focus and touch what I really have too. And leave the rest to cope on its own.

 

[Conort2]

What the hell? So I have to watch out for Prime overdose and avoid vacuuming the gravel as well?

So what do I do now? Do I create a bare bottom tank then or what substrate should I do?

I’d personally use sand. Corydoras ideally need sand to exhibit natural behaviour of digging and sand sifting. Gravel doesn’t allow this and I wouldn’t keep corydoras on anything other than sand, it’s not fair on the fish in my opinion.

Gravel also traps a massive amount of detritus and waste. This doesn’t happen with sand as the waste simply sits on top where it can easily be siphoned away.

 

[_Maq_]

Gravel also traps a massive amount of detritus and waste. This doesn’t happen with sand as the waste simply sits on top where it can easily be siphoned away.

It looks like this but I believe the reality is different.
Detritus gets transformed in very small particles during decomposition and penetrates even into soft substrate. And detritus also evolves if the substrate itself - decaying roots, dead microbes. In my tanks with soft sand there's no detritus on the surface but lots of it appear when I touch the substrate.

 

[dw1305]

Hi all,

So what do I do now? Do I create a bare bottom tank then or what substrate should I do?

I agree with the other posters. Have a sand substrate and <"leave it relatively undisturbed">?

There is an explanation of why in Stephan Tanner's article - <"Aquarium Biofiltration - SWISSTROPICALS">. This is @Nont's emersed Echinodorus, which shows <"why roots are so important">.

I use sand a couple of centimetres thick, but I have very heavily planted tanks and Malaysian Trumpet Snails (Melanoides tuberculata).

If I had fewer plants I would just have a cosmetic layer of sand.

cheers Darrel

 

[Conort2]

In my tanks with soft sand there's no detritus on the surface but lots of it appear when I touch the substrate

that’s interesting, it doesn’t seem to be the case in my tanks. However, every tank has corydoras in it and also Malaysian trumpet snails so I’m sure they both do a good job of shifting the detritus up into the water column to be removed by mechanical filtration.

 

[tam]

I think surface detritus is more down to individual tank flow, often there is a spot that collects it and the rest is clear but if there is less flow in visible areas you'll see it more.

I only have one tank with sand (about 1" deep) and I can't vacuum it - there are too many fine roots sitting mm below the suface. If I disturb the substrate they are then sticking out like worms and look very messy and gather detritus/grow algae. I end up spending ages trying to push them all back down.