Cardinal tetras acting strange

We have a 30 gallon tank. It has been running with 7 dwarf corys, 7 harlequin rasboras, and 7 ember tetras for 3 months. It has been going well with weekly water changes of about 30%. We recently added 7 cardinal tetras and a cocatoo cichlid. All went well the first two weeks after adding the cockatoo and the cardinals with 30% water changes. Then, a few nights ago the cardinals starting hiding a lot and losing color. I forgot to check the levels until I had done about a 30% water change, but at that point the nitrates were still around 20ppm. Ammonia was 0, nitrite was 0. At the same time, I noticed that the filter was barely running...not sure if that was a new thing or if I had just bumped the control button to a very low level during cleaning. I use an AquaClear 30 and a sponge filter in the tank. I continued to do a change the water, getting ammonia, nitrites, and nitrates down to 0.

The cardinals looked fine for a couple of days again. But now they are back to hiding. Not losing color, but hiding. And not darting to the top to eat. No other fish appear affected. Ammonia currently 0, nitrites 0, nitrates between 0 and 5.

I did not do enough homework and the ph may be too high. It runs around 7.4. Or, they may just be recovering from a high nitrate level. I am guessing that the high nitrates was due to the filter not running well. Not sure why else it would have risen so high. I had done a water change less of 30% less than a week before. Any thoughts would be great!

 

If your filter was not working properly you would have had high ammonia or high nitrites, not high nitrates.

As you probably know there is bacteria in your filter that converts ammonia into nitrites and nitrites into nitrates. So the more ammonia being processed, the more nitrates you end up with. And the only way to effectively reduce nitrates is thru weekly partial water changes. And now that you have increased the number of fish in your tank, you are getting more ammonia, which means more nitrites which means more nitrates. So you may have to do a larger weekly water change to keep the nitrates down to an acceptable level. BTW if you have 0ppm nitrates inyour tap water, ideally you would want to keep your nitrates under 20ppm.

I've never kept cichlids, but many are aggressive and I wonder of your fish are hiding because they are stressed out by the cichlid. There doesn't seem to be anything with your water parameters that would cause your fish to hide.

 

I do believe that Cockatoo Cichlids, if given the right space will be peaceful. In a 30 gal, it is probably very territorial, so the others may be affected, that is if the nitrites and ammonia levels are not high. Probably you should either add more hiding spots or upgrade to a 40-55 gal


"Loving a pet is not enough, you have to discipline it, feed it and treat them when they are sick."
-Cacret

 

When going to sleep (you're talking about night) cardinals loose color and hide between the plants totally normal.
During the day they don't like to be in open water if the substrate is lightcolored and/or lights are too bright. They are dark colored on their back, so they aren't visible when they are above natural / dark substrate.
Sollution : dark substrate or floatingplants.

 

Thanks for the replies. They look better but their behavior varies day to day. I have dark substrate and lots of silk plants, as well as a few real plants. Also a couple of caves. I could certainly add more, but can't get a larger tank at this time. If needed, we will return the cockatoo To the LFS. Love having this forum to come to!

 

They won't really use caves.
They live in dark waters so can be shy in our "clear, bright" tanks. Keep them warm !!! Nice fish

 

I turned the heater up a few degrees and that seems to be helping. I had turned it down, so maybe that was part of the problem. Thanks