Hi, im new on this and really need some help!

About 4 months ago, we bought a 35L cold water fish tank. After about a month (we had a few troubles with the water at the beginning) we gradually introduced 5 mountain minnows and left it as this for about a couple of months. We then decided to get 2 plecs (only small ones) and ever since, we’ve had nothing but trouble with the water!

Our Nitrite and Ammonia levels have increased quite a lot:-
Nitrite – 3.3mg (!)
Ammonia – 1.2mg
The water is also cloudy and there is brown algae apparent.

The fish all seem completely fine in both physical and behavioural characteristics. We can’t see any changes at all. We asked at the store we bought them from and they said that our filter may not be coping with the waste. So we bought an internal filter about a week or so ago. But it’s getting worse! We told them this and they have no idea what is happening here.

We don’t feed the fish much – in fact I didn’t feed them this morning as someone suggested not doing it for a couple of days and seeing if this helps (Is this a good idea?).

We’re doing 10 – 15% water changes once every week – should we increase this!?

What are we doing wrong and how can we improve our water quality so that it is safe for the fish?

Thanks

I seriously doubt the filter is able to cope with the waste, given that the tank is technically overstocked with the 'Plecs'. This would clearly explain the cloudy water (bacterial bloom or excess silicates/TDS) and the brown algae (caused by excess nutrients, silicates or low dissolved oxygen levels).

Those 'Plecs' that you have are more than likely Balitoridae Hillstream Loaches. The most commonly sold species shouldn't really be in a 35 litre tank and they do need cool, fast and highly-oxygenated water; a lot of fishkeepers aren't aware of these basic requirements. Aquatic stores mis-label these fish as 'Plecs' (which are South American Catfish from the family Loricariidae) because of a lack of knowledge in properly identifying the species.

With ammonia and nitrite above 0ppm (concentrations of 1.2mg/l. and 3.3mg/l. are lethal) you need to step up the water changes to 50% daily to bring them back to safe levels.

Hi, thanks for replying - I was really hoping someone would!

I just had a little google on those Balitoridae Hillstream Loaches' and they don't really look like them. This is what they were labelled as in the store and they look pretty much exactly the same as these. Gold Spot Dwarf Pleco - Parotocinclus spilosoma

If the plecs or whatever they are do need a bigger tank and better filtration then is there any point in doing the 50% water changes until it gets better if the fish are still in there? Surely it will only get worse again?

If the store has sold you Parotocinclus spilosoma then they shouldn't have done if they had the knowledge of the size of your tank and the fact that you have White Cloud Mountain Minnows which are coldwater fish whereas Plecs thrive in warmer conditions.

The fish could be dead if you don't step up the water changes, removing the Plecs won't make much of a difference to the water quality if the filter can't cope with the level of ammonia.

the plecs are going to get way way to big for your tank! If your wanting something to eat the algae and keep the tank slightly cleaner then a temperate golden apple snail would have been a better choice.

As for the water changes i do 30% once a week on my standard cold water and tropical tanks.

My planted tank / shrimp tank gets 50% change every 4 days

My marine tank gets 15% change once a week

I was doing bigger water changes in the marine tank but my corals were suffering and not extending how they should.

Take your plecs back for either a swap or a refund.

The odds are, they will since aquatic stores constantly mis-label species before selling them.

They don't look anything like any other Plec I've looked up but pretty much identical to the Dwarf Pleco's. Every website I have been on is saying they don't grow more than a couple of inches.
Anyway I will just have to wait and see what happens.

Also one of the pleco's decided to kill himself - too hard to explain how and I'm sure you don't wanna know anyway.

I carried on doing 50% water changes and everything went down to what it was supposed to be. So I now have a happy tank

Thanks for the advice everyone