My oscar recently had a number of scrapes which I guesss were from the lava rock in the aquarium and he started to act depressed (sitting on the bottom and not eating) so last weekend I gave the tank an overhaul - I took out 99% of the lava, and instead added 4 plants, slate and some wood - I also bought a scraper and cleaned the back of the tank that had been covered in algae for the past year (my scrubbing brush wash fine for the front and sides but I couldn't get to the back).

Now I have the following problems: the Oscar hasn't eaten all week, he fights his reflection in the back of the now clean glass, he has a cut on his head that appears like it may have bled and he just violently uprooted a plant.

He doesn't appear too depressed as he swims around, but at feeding time he cowers in the bottom corner (he's never done this before) and when I go to the aquarium he backs away from me and tries to hide beind a plant or stone.

My biggest concern is that he won't eat and his behaviour is strange.

I tested the water and I got:
7-8 on ph (seems fine)
0.1 in Ammonia (fine)
0 - 0.1 Nitrite (fine)

BUT 100mg on nitrate. I'm going to buy a reccommended sachet tomorrow to reduce this (although I don't understand why it's so high, I did a water change last weekend of about 20%).

Any suggestions please, I just want my fish to start eating again and return to his perfectly normal healthy self that he's been for the past 14 months since I got him.

What is your tank size, feeding regime and do you take you all the uneaten food out?

Nitrate level of 100 will cause stress to a fish which is why they won't eat sometimes.

The best way of reducing nitrate levels is by carrying out water changes. I should try this before you start adding chemicals. You might want to check your tap water for nitrate levels.

You ammonia and nitrite are too high, you should have zero readings. Any readings of these toxins will cause stress to a fish, even if you don't notice anything.

I should reduce feeding for the moment and concentrate on getting your water back to an acceptable level. Fish can go without food for quite a long time to don't worry. Maybe try some of food every other day and only a small amount

Your ammonia and nitrite should be zero. Retest again. If its not zero then something is wrong and you may have to recycle. However they are on the low side of the readings but keep testing them and keep a very close eye on the levels. Ammonia and nitrite are poisionus to oscars.


The best way to reduce nitrates is water change. To prove it test your water, then do a 50% water change and retest. Do a 50% water change everyday until your levels are down to below 40 preferably max 20


I am guessing that your oscar is backing away etc from you because you have done something that you usually dont do i.e. cleaning the back of the tank and he isnt sure of you anymore and is worried. He will soon get used to the normal soon. There is nothing wrong putting your hand is the tank and getting him used to it. Also oscars uproot plants from the substrate- its normal. Thats why most people dont put plants in with oscars. I myself find that you can get away with plastic plants with suckers. I use these to cover filter pipes and heaters



Over feeding can cause nitrate to get too high. I wouldnt bother feeding your oscar till he starts begging for food again- hunger will soon sort him out. Also when feeding only feed once a day and only what he will eat in 3 to 5 mins. Try adding myxazin for the wound if you are worried about it

Your oscar is fighting his reflection because he thinks its another fish- dont worry about it