Dead Fish - What Should I Do?

[David J]

Hi

Ok, here's the bullet points of what's been going on.

I have a 90L tank, fully cycled. First fish went in about 3 months ago, lemon tetras. Since then I've added glowlight tetra and panda cory's.

Water stats have been fine for months. I do at least one 25% water change every week but usually do 2.

2 days ago I installed a fluval 206 external filter to replace my fluval U2 internal. For safety sake I left the internal running in the tank until I as sure the new one was running ok then it was my intention to move the mature media from the internal to the external to seed the new media.

Since installing the new filter (with a spray bar), I've been concerned about the stronger current in the tank. The fish seemed fine but you could see they were having to work a bit harder. To reduce the flow, today I widened the holes in the spraybar and added an extra hole. This certainly reduced the flow and the fish seemed happier. That was about 5 hours ago.

I've just found a dead lemon tetra. I've tested the water. Ammonia is zero as is nitrite. Nitrate is at about 20ppm. I usually do a water change on a Tuesday. The other fish seem ok except the lemon tetras mouths are opening and closing quicker than before I think.

I have turned off the external for now and left the internal running. I did this because I can only assume it is something to do with the water flow being higher.

It could be that this lemon would've died anyway and had nothing to do with the new filter but how do I know. I don't want more deaths. Any ideas anyone?

Many thanks,

David

 

[snazy]

I don't think the flow had anything to do with it. I've kept very high flow, even with fry and none died.
Do you have enough surface movement on top of the water for oxygen?
Also, don't rely on tests so much. They aren't accurate so doing a water change when you see an issue is best.
It could be a coincidence. Just keep an eye.

 

[David J]

Hi

Thank you for the reply.

Regarding surface agitation, I have the spray bar positioned on the side wall bout 1-2 inches under the water. When I first put it in I saw that there was a strong ripple on the water but no bubbles or broken surface at all so I raised one end of the bar until on hole was at the surface. This resulted in broken water and bubbles under the surface. My internal has the Venturi feature and created bubbles. The new spray bar creates more bubbles than the old system, roughly double.

I've put everything back to the way it was before installing the external for now and will monitor. I hope it is just a coincidence.

Thanks

 

[snazy]

Your fish may have suffered from a bad water quality for a long time and just gave up on the wrong day, considering you've got just one U2 small filter in 90L tank.
I'd keep the external running. You don't need bubbles on the surface, you need ripples so it moves the water enough constantly.

 

[David J]

I see your point but I don't think the water has been bad because my water tests have been really good since my cycle finished, but like you said before, test results aren't always reliable so who knows. The U2 should be fine for the size of tank along with the number of fish i have. I'm upgrading to an external before adding some more fish.

I'll put the external back on tomorrow morning cops its too late now. Thanks very much for your time snazy. I'll post again tomorrow with the situation.

David.

 

[snazy]

It's a good idea to upgrade anyway. I have 2 U2 filters and use them in way smaller tanks. It's a tad too small and although I find them efficient for the size, I wouldn't rely on one for a fully stocked 90L tank. I'd leave the U2 filter in there along the external for at least 2 months, or just transfer all the media from it to the external and monitor the water.
Hope your fish are ok and that's just a one off.

 

[David J]

Hi

Ok, almost 24 hours later and no further fish lost. I have just put the external back on now after switching back to the internal last night. I think it was just a coincidence. Time will tell.

I'm going to make a new thread on another board regarding flow rates etc. I'm doing it on another board as this is no longer an 'emergency'.

Thanks again for the advice,

David.

 

[KirkyArcher]

Did you try reducing the flow by using the tap on the aqua stop valve? It's by far the easiest way to reduce flow rate.

 

[David J]

Did you try reducing the flow by using the tap on the aqua stop valve? It's by far the easiest way to reduce flow rate.

Hi, yeah I did that and it does reduce it a little but also made the filter louder which bugged me.
 

I think what happened was just a coincidence. Tetras are easy to maintain aquarium fish and are tolerable to almost any water parameters the common hobbyist maintains.
 
 
Alan Young
<mod edit>

Hi, that's funny because I was thinking that too. The lemon tetras are apparently on of the hardiest so it would be surprising if what I've done has caused this. As time goes by I'm getting more confident in the new equipment. I'm running both filters for another couple of days and will then swap the media and remove the internal.

Thanks for the replies folks.

David.