2 Fish Dead In My Cichlid Tank! How?

[thabigo]

So i have a Aqueon 36 Gallon with a 70 Aqua Clear Filter
 
Water Temp: 76 Degrees F
Lighting: 17 Watt T8 Full Spectrum Bulb (Came with Tank Kit)
Current Stock:
1 Red Zebra
1 Electric Yellow 
1 Duboisi 
1 demasoni
3 Tiger Barbs
1 Bristle Nose Pleco
1 Rubber Nose Pleco
 
My Bristle Nose Pleco died and my Duboisi Cichlid I just found dead today. This must have happened withing the past 24 hours. A water Change was done on Tuesday the 19th. Not sure what could of caused it. I changed 10 Gallons so that is about 27% water change. I made sure the Temperature was the same around 75-77 degrees. The only main difference is that my water is @ a 8.0 Ph level and my Tap water comes out @ 7.4. But I have had the Pleco for about 2 weeks now and the Duboisi for a little over a month now. Not Sure what could have been the issue.
 
What do you guys think it could be? I just tested all my water Parameters and it all read the same. 8.0 Ph, 0 Ammonia, 0 Nitrites, and around 10-20 Nitrates. Nothing out of the ordinary there. So any advice i would greatly appreciate it. I also just recently added 1 Mystery Snail, and 2 Nerite Snails a few days ago to help battle my brown algae I am getting in my tank. But i don't think that would cause anything bad in my tank.

 

[RRaquariums]

First off I'm not trying to sound like a jerk or tell you what to do I'll just give you my opinion based on my experience with cichlids.

Alright so here's the deal when it comes to African cichlids they are a bit tricky.
You have a very wide range of African cichlids so I'll address that first the electric yellow, demasoni and red zebra are all from lake Malawi and are compatible they grow to about the same size eat mostly the same food they are all omnivores except the demasoni who is more of a herbivore but they pretty much have the same amounts of aggressiveness so they should all do ok together provided you have a good amount of hiding places.
Here's where your trouble comes in you added a Duboisi cichlid they come from lake Tanganyika which is a completly different lake plus they are a much less agressive fish who prefers a calmer tank with many of it's own kind as tank mates it is also a herbivore that needs a diet high in vegetable matter like seaweed and fresh lettuce daily supplemented with high quality vegetable bases dry food. On top of that they require a tank of at least 50 gallons.
So to me the reason he died is because he was in a tank alone with more agressive fish and make no mistake African cichlids will kill any fish weaker then them so my suggestion would be stick with the Malawi cichlids since they tend to get along with other Malawis like you have.
As for the bristlenose same reason nothing really goes with African cichlids but African cichlids so if it where me I'd rehome the pleco you still have and the tiger barbs since when the cichlids get big enough they will kill them to.

Sorry if this all seems negative again I'm not passing any judgment it's a very easy mistake to make when dealing with African cichlids I know I made a few mistakes with what cichlids are compatible when I started so your not alone.

 

[thabigo]

That's interesting because I started my Tank with the 3 Barbs to get my tank cycled then I added the 3 African Chilids, The Red Zebra, Electric Yellow, and a Elongate Mbuna. The E. Mbuna was bigger then the other Two and he kept harassing the other two Cichlids, The Barbs were always fine. It came to the point that my Red Zebra was swimming weird and developed an Ulcer on his right side of his stomach, (I still have him in a 5 gallon w/ Primafix healing). I then bought the other two Cichlids, the Demasoni and the Duboisi.
 
The E Mbuna was going after both of them. It lasted for about a day then I just decided to take him out of that tank and take him back to the pet store. From that point foward everyone was happy. I had no issues, water quality was good, Changing about every 1.5 - 2 weeks. Although the Demasoni seems like he lost his appetite but that might be because all I have been feeding is flakes and cichlid pellets. I might look into some more Herbivore Diets for him.
However, the Duboisi was eating everything fine, he had normal behaviors was swimming good and active. It seemed like after that one water change I just did back on Tuesday he became more shy and I didn't see him as much and he wasn't coming up to eat when it was feeding time. So I am not sure what could of happened, maybe it was just a coincidence and the stress caught up to him but I guess it is very hard to diagnose when a fish dies..
 
I appreciate your advice and I will look into maybe adding a few more Cichlids but make sure they are from Lake Malawis.