Hiya,i bought my boyfriend an aquastart 320 fishtank (28L) for christamas.
It has an undergravel filter,heater etc.
We set the tank up and left it for a week to run etc,and added a pair of dwarf gouramis and 2 corys.
he now only has the male gourami and 1 cory,
The nitrate levels are through the roof,and even with a 25% water change every other day(as advised by the people at the aquarium place) the nitrate levels will not go down.
we did a full change a week ago,cleaned everything properly,put the fish back in and the nitrate levels were fine for 48hours then went back up again.
Iv`e kept fish all my life and have never had this problem ever!!!
We are running out of things to do.
I know we have probably done something wrong somewhere along the line,can anyone give any advise?

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Fudge,my American Cocker Spaniel

Hi

What is the exact reading you are getting for Nitrate? And do you have readings for Ammonia and NitrITE aswell?

Unfortunately, just leaving the tank for a week to run doesn't actually do anything useful. Ideally you should have cycled the tank as described here - Frequently asked questions on fishless cycling | Practical Fishkeeping magazine - in order to mature your filter so it could cope with the waste produced by your fish.

When you say you did a 'full change' a week ago and cleaned everything, what exactly did you do? I'm assuming that if you've kept fish before, you know not to empty the tank and clean everything with fresh water? Coz that would effectively kill any good bacteria that had started to build up!

Anyways, I don't know masses about this type of thing myself, but hopefully someone else more knowledgeable will come along and we'll be able to make sure you don't lose any more fish!

judging by the size of the tank not only has it not been cycled properly but you have stocked it to quickly too.

I did not do a fishless cycle i got mollies to cycle my tank and they did real well but i was changing water every other day around 25%.

I am thinking it must be ammonia and nitrites that have killed off your fish although i do not know without the readings.

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As the others have said, a week isn't long enough. The cycling process can take several weeks to complete. Tanks that haven't been cycled will develop new tank syndrome (NTS) which causes large spikes in ammonia and nitrite, these two toxins can easily kill fish.

I would recommend that you cut out the feeding for a while and test the water for ammonia, nitrite and pH. Also when you carried out the water changes did you use dechlorinated water.

Nitrate isn't as toxic as ammonia and nitrite however high levels can inhibit growth and ultimately lower the fishes immune system.

As for the Dwarf gouramis, I agree 100% with FishyFins. These fish aren't as hardy as they used to be and are quite susceptible to Dwarf gourami iridovirus (DGIV) among other diseases.

I can't really add to what anyone else has said in detail but I would or rather would have tried plants in the tank when you were cycling the tank.

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