Help The Suffering Fish!

[rbnfrance]

Hello to all,

We have had a tropical tank for over 3 months now. We have, I believe, been through the cycling process, and have suddenly got to a stage where several fish have died in a short space of time. I can see no obvious sign of disease. About 6 weeks ago we got a new covering of brown algae. We have continued to do water changes, but I have just done a test and found that the ph level is higher than usual at 7.8, Ammonia is 0, Nitrite is 0, and Nitrate is much higher than normal at (difficult to say from the colour but certainly above 80, probably 100 to 140ppm. Another clue is that the brown algae is slowly being replaced by green algae. I thought that this was a good thing.

We stock Platy's, Guppy's, Zeb Danio's, Tiger Barb's. The tank is 108 litres. Some of the other fish are breathing quite quickly.

Many Thanks for any advice you can give.

 

[ZoddyZod]

the algae should not be an issue.

Fish breathing rapidly could mean a lack of oxygen. Is your filter disturbing the water surface sufficiently?

 

[the_lock_man]

I'd say, from the nitrate levels, that you aren't doing enough water changes, either in terms of frequency or amount. But this probably wouldn't explain the fish breathing quickly. This could be, as Zod says, lack of oxygenation. It could also be damage to the gills from previous exposure to ammonia. Given that nitrate levels are on the high side, it suggests that you might not have kept right on top of ammonia levels during the cycling process. If so, it might also be the reason for recent deaths.

 

[rbnfrance]

Thanks for your responses. The filter is disturbing the surface, and I have 2 airstones working at a low level. We did do regular water changes when the ammonia was higher, but I guess that its possible that they were damaged, as you suggest. I would stress that this is quite a sudden change however. Do you know why the PH has gone up? Is that related to the Nitrates? Also, given that the fish are fragile at the moment, should I do a water change and what percentage for a tank this size (108 l)

Many thanks once again.

 

[the_lock_man]

How big a change in pH was it? If the change happened very quickly, that may be what killed the other fish. As for the reason, that's a difficult one - do you have any alkaline rocks or gravel in the tank, could any chalk have got into your water supply?

I'd suggest that you do need to change the water, to get the nitrate down, as this won't be helping matters. The problem is that if your tap water chemistry is a fair bit different from your tank water chemistry, a single big change could cause further problems.

I'd say start off doing hourly water changes

1) 10%
2) 10%
3) 15%
4) 15%
5) 20%
6) 20%

and that should see the nitrate down to around 50ppm, without affecting pH, KH, etc., too much.

 

[rbnfrance]

How big a change in pH was it? If the change happened very quickly, that may be what killed the other fish. As for the reason, that's a difficult one - do you have any alkaline rocks or gravel in the tank, could any chalk have got into your water supply?

I'd suggest that you do need to change the water, to get the nitrate down, as this won't be helping matters. The problem is that if your tap water chemistry is a fair bit different from your tank water chemistry, a single big change could cause further problems.

I'd say start off doing hourly water changes

1) 10%
2) 10%
3) 15%
4) 15%
5) 20%
6) 20%

and that should see the nitrate down to around 50ppm, without affecting pH, KH, etc., too much.

PH is usually 7.4, so it has gone up by .4. I haven't tested for a while so not sure how sudden it was. I do have gravel in the tank and I'm trying to get hold of a gravel vacuum, but I live in China and they are hard to find. I may change the gravel for something else, but I don't think the gravel is alkaline. I will do as you suggest, and thanks for the advice. Just to be sure, that is hourly water changes?

 

[CezzaXV]

Have you tested your tap water? Would be worth knowing how much nitrate is in your tap water.

 

[OldMan47]

A pH of 7.8 is not a problem for your fish. It is the pH in most of my tanks and I keep all but the barbs with no problem. If fish are gasping, you have a water quality problem, no matter what your tests tell you. Do a huge, over 50%, water change and observe the fish. They may tell you that another large water change is in order or they may tell you that you have done enough for now.