Black stuff in gravel, and dead/dying fish (and shrimp, and snails)

[exscape]

First off, I apologize if my terminology is off. Please ask for clarification if you need it to understand something. English is not my native language, and I virtually never read about aquarium stuff in English, so I had to translate many aquarium/fish-specific terms!

I'm helping take care of a 160 liter (42 gallon) freshwater aquarium, housing a variety of different life.
It has about two dozen of a guppy variant (Endler's livebearer, Poecilia wingei), a few Lyretail killifish (Aphyosemion australe, 1 male, 3 female), one clown killifish, three L catfishes (one L128 and two sold as L201 that likely aren't), some shrimp (white pearl and 2 Amano), and a few snail variants, most of them tiny (about 1/4 inch).

The catfishes were purchased a few weeks back, along with some sinking pellets for them to eat.
Though I'm not certain of the connection, it seems that some pellets went uneaten, and since then (OR possibly since before), there's some black stuff in the bottom gravel. It's a fair amount, though; I doubt that all of it is simply uneaten food! My GF, who has the aquarium, is well aware of overfeeding issues, and AFAIK hasn't used the pellets very much since she noticed they weren't eaten.

In the past week, especially the past few days, most of the life in the aquarium has started to get sick.
One australe male plus a clown killifish died last week, and we found a dead shrimp yesterday, along with a sick one.
The dead ones last week were found the day after a water change and cleaning of the internal filter, where some (or a lot) of bad stuff from the filter came out into the water during the filter removal.

Today, plenty of the snails were headed for above the water level, and an australe female is lying on the bottom gravel, alive but clearly not well. The fully grown australe female looks fine to me, and the third one I'm unsure about, but she seems to have some energy, at least.
Another water change was performed, but with no apparent effect on the dying australe female. The others seem better to me, though.

Test strips seems to indicate that the water quality is good -- according to the parameters measured, of course.

The most recent one, from this morning, shows:

Nitrate 0
Nitrite OK
GH (General hardness) 4-7 degrees
KH (carbonates) 6 degrees
pH 6.8
Cl2 0

I hope that's enough info. I'm sure more can be provided if necessary.

I feel that in order to get rid of the black stuff, the aquarium might have to be fully emptied of plants, fish and decorations, and that's no easy task. Plus, there's only a 86 L aquarium (half of the current one) available to put them in temporarily.

Does anyone have any advice on what to do to take care of this?

 

[mambee]

Please test your water again. Ammonia and nitrite should be 0. If your nitrate is 0, then your tank isn't cycled and that is causing the problem. The cycle is ammonia to nitrite to nitrate. I would perform 50% water changes daily (adding water conditioner) until you start to register some nitrates. Maybe you killed the beneficial bacteria when you cleaned the filter?

 

[exscape]

Hmm, that sounds weird. I looked through the log, and nitrate (NO3) has tested as 0 every time this year, perhaps 8-9 times or so total. There haven't been many issues prior to the past few weeks, though.

I assume water conditioner is the stuff that removes chlorine/chloramines, copper and such? Rather than the stuff that contains beneficial bacteria?

 

[mambee]

Nitrate is unlikely to be zero. Maybe try a different test kit.

Yes, I meant the stuff that removes chlorine/chloramines.

 

[Toad]

When is the last time you gravel vacumned?

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[exscape]

When is the last time you gravel vacumned?

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That depends, how thorough a cleaning are we talking about?
The top layer (what is reachable of it) is cleaned once a week, during water changes.
The bottom layer(s) and especially stuff below various rocks, caves and plants, on the other hand, are probably almost never cleaned.

 

[Toad]

I'd say do a thorough cleaning of that stuff, if you have stuff rotting enough to cause a problem, it's not going to get better until it's out of the tank

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[guppygourami]

First of all, your English is great! Much better than some 'native speakers' that I've met too

Now I agree with Toad on the gravel cleanings. My fish are always hungry and will eat anything but there are always leftovers. I do gravel cleanings bi-weekly or more often. I'd say that about three gravel cleanings later you'll notice a big change. Let us know how it goes!

Also, excess food can be netted out on a daily basis but gravel cleanings are more thorough and will get under the gravel.


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[exscape]

Alright, thanks!

Is it safe to take care of that with everything still in there? Seeing how the last filter cleaning killed multiple fish, I'm rather wary of starting to mix stuff around too much.

It does seem to be going better the past few days, though. Several of the fish have been moved to a new aquarium (for other reasons), and a ~50% water change was performed during that move, since aquarium water was needed for the new aquarium.
That said, I will indeed look into cleaning the gravel more thoroughly (but also carefully).

 

[guppygourami]

Alright, thanks!



Is it safe to take care of that with everything still in there? Seeing how the last filter cleaning killed multiple fish, I'm rather wary of starting to mix stuff around too much.



It does seem to be going better the past few days, though. Several of the fish have been moved to a new aquarium (for other reasons), and a ~50% water change was performed during that move, since aquarium water was needed for the new aquarium.

That said, I will indeed look into cleaning the gravel more thoroughly (but also carefully).

Good to hear that things are going better. And what happened with the filter cleaning? What type of filter? I have a AQ50 and as long as you don't change the filters and just rinse them the fish are fine. I would recommend unplugging the filter(may result in breaking it), heater (possibility of a malfunction) and light (I've burnt myself one too many times before...) before cleaning. My fish have never been sucked in and there's a part of my siphon that pushes fish back in if they were to get sucked into the first tube. Even if your fish were to get sucked in you could just net it back in Tell us how it goes!


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[exscape]

Good to hear that things are going better. And what happened with the filter cleaning? What type of filter? I have a AQ50 and as long as you don't change the filters and just rinse them the fish are fine. I would recommend unplugging the filter(may result in breaking it), heater (possibility of a malfunction) and light (I've burnt myself one too many times before...) before cleaning. My fish have never been sucked in and there's a part of my siphon that pushes fish back in if they were to get sucked into the first tube. Even if your fish were to get sucked in you could just net it back in Tell us how it goes!

The filter is a semi-DIY internal filter, with a big sponge material around the entire outside (including where the water is sucked in) to act as the filter media.

During the last cleaning, the filter was full of particles and dirt (including the black stuff), and quite a bit was accidentally released into the water during the mechanical removal of the filter.
The cleaning itself was performed in aquarium water and went without issue.

My worry with the vacuuming is that more stuff will be released from the bottom gravel (where it likely doesn't cause much harm) into the water (where it likely does), but I'll give it a try while carefully keeping track of how much dirt escapes into the water.

 

[guppygourami]

The filter is a semi-DIY internal filter, with a big sponge material around the entire outside (including where the water is sucked in) to act as the filter media.



During the last cleaning, the filter was full of particles and dirt (including the black stuff), and quite a bit was accidentally released into the water during the mechanical removal of the filter.

The cleaning itself was performed in aquarium water and went without issue.



My worry with the vacuuming is that more stuff will be released from the bottom gravel (where it likely doesn't cause much harm) into the water (where it likely does), but I'll give it a try while carefully keeping track of how much dirt escapes into the water.

Oh I think I understand now. With the gravel vac you can temporarily put your fish in some sort of bucket for a little while with aquarium water and they'll be fine. I hadn't vaccuumed for a whole year once but my fish were fine even through debris and other gross stuff was flying in their faces.


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