Dying Otos...

[plantmania]

For a week, all my otos have been dying.... Either in pairs or in ones.... Some otos are with me for more than a year, some I recently added...

A grand total of 8 otos had died. The only difference from my schedule is that I changed to use Aquaplus from nutrafin as my water conditioner instead of Tetra's aquasafe NH/CL....

Anyone know the reasons that ONLY my Otos died?

1) It's a community 4ft x 2.5 x 2.5 tank with discus(5), cardinal tetra(50+), clown loach(5), holland ram (1), rainbow fish (4), and corydoras(5).

2) The water parameters are typical of a fresh soft water tropical tank. ph 6.8, gH 2, kH 3, very low concentration of nitrates/ammonia and nitrites...

3) No noticable deformation on the otos.... some even looked well-fed. Only thing I observed is that they became very inactive. Some deaths are only noticed when discus starts to peck on the dead body to feed on its eyes, its body is too hard to eat....

4) I will occassionally add aquarium salt , about 1 tablespoon per 10-20 gallon.... Using the same brand for a few years.

5) Dosage of Aquaplus is 60 ml for every water change of about 200 litres of water. Weekly.

6) I use a UV sterilizer , Ecoaqualizer and a Canister filter....

Any advice on the critical needs of an Oto ? Hate to lose them.... Know any labs to test out the water ???

[Kingfisher]

I have been using AquaPlus since the start of my tank. Only recently have my Zebra Otos been dying. Lost 4 of them although the normal Otos are fine. The Xebra Otos has been with me for many months already.

[plantmania]

I found a possible cause of deaths....

At night, I found some of my fishes hanging near the water surface.... It appears that they have difficulty breathing, as if the oxygen content is not sufficient. I found the last of my holland ram died due to suffocation after I added only one-tenth of a recommended dosage for anti-internal bacteria medication(it's reduces oxygen absorption in the water). Take note that I have aeration on all the time....The herbal or chemical component of aquaplus might have some effects on the gills of fish.... not very sure. Otos are high-oxygen loving fishes....

Anyway, will stop using Aquaplus once I finish my big 2Litres bottle or when deaths increase anymore for next few weeks..... Then switch back to Aquasafe. Note that I don't work for any company from the aquarium trade.

Found an article about water conditioners....
http://www.thetropicaltank.co.uk/rev-cond.htm
A note about "stress coating" from the article :

One of the main reasons for the first question above is the concept that anything which sticks to the body tissues of fishes might also stick to the gill tissue and inhibit the function of the gills, or even suffocate the fish

Apparently Tetra's Aquasafe NH/CL is the best complete removal....[/quote]