Need help

What did the dead fish look like?
Do you have any pictures of them when they died?

Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the tank?

What sort of filter is on the tank?
How often and how do you clean the filter?

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The dark green slime on the glass is blue green algae (Cyanobacter bacteria). This stuff loves nutrients, red light, low oxygen levels, and slow water movement. Reducing the dry food going into the tank and doing bigger water changes and gravel cleaning the substrate should clear it up.

The black fluffy stuff on the plants is black beard algae. It grows from too many nutrients and is a pain to deal with. Bigger water changes and gravel cleaning can help.

The brown stuff on the glass can be blue green algae or brown algae. Just wipe it off with a clean sponge.

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A single big water change each week is better than lots of little ones.

If you add aquarium plant fertiliser each week, you should do a big water change before adding more fertiliser. If you don't, the residual fertilsier that hasn't been used, can build up and over time poison fish or encourage algae problems (much like what you have now). Doing a big water change before adding more fertiliser dilutes any remaining nutrients and reduces the risk of poisoning or an imbalance in the nutrients in the water.

If you do a 20% water change each week you leave behind 80% of the bad stuff in the water.
If you do a 50% water change each week you leave behind 50% of the bad stuff in the water.
If you do a 75% water change each week you leave behind 25% of the bad stuff in the water.

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You need a picture on the back of the tank to make the fish feel more secure. You can buy aquarium backings from any pet shop or online, or use a plastic bin liner or some coloured card and tape it to the outside on the back of the tank.

Thank you for you reply. So tomorrow I’m going to do a clean , so if I do a 50% change and I use an electric vacuum too which I always use , and give the glass a good clean. So the water I use is tap water do I put the tank safe in the water before I put it in the tank?? I’ve taken a photo of my filter and I always clean the sponges out in the dirty water. I put up. Photo of the lighting too , can you tell me if it looks ok?

Big big thank you for your help.

Claudie said:

So the water I use is tap water do I put the tank safe in the water before I put it in the tank??

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That depends on whether you refill with a bucket or a hose.

With a bucket, add the dechlorinator to each bucketful at the dose rate for the amount of water in the bucket. For example, I put 7.6 litres water in a 10 gallon bucket and add enough dechlorinator to that 7.6 litres (it as odd amount as 7.6 litres = 2 US gallons). Put the dechlorinator in the bucket and run the water in on top of it as that mixes it in better.

With a hose, add enough dechlorinator to treat all the new water to the tank before starting to run the new water in.



Additionally, if you have a combi boiler you can mix hot and cold tap water to get the temperature right. If you have a hot water cylinder with a header tank in the attic and fill with a bucket, boil water in a kettle to get the temp of each bucketful right.

Am I doing it right by cleaning the sponges out in the dirty water and also do you think my lighting it right

Cleaning media in old tank water is perfect


Re the lighting, I have lights that just turn on and off, I can't alter the colours or intensity so I have no experience with those, I'm afraid. But in general terms, try 7 hours at full strength and cut down the blue-only at the end as blue encourages algae. Plants can't use just blue light but algae can.

One more question and I promise that will be it for now lol how often do I change the the filters?

That depends what's in the filter.

Sponges only need changing when they go into holes or won't go back to shape after squeezing. They last for years.
Ceramic media needs changing when it starts to crumble, again it'll last for years.
Wool/floss (looks like pillow stuffing) gets clogged easily and doesn't wash properly so needs changing when it goes shapeless, usually after just a few washings. If you have this, don't buy the floss sold by the filter manufacturer. It's much cheaper to buy a length off a roll (eBay Amazon sell it) and cut it to shape.
Carbon should be changed frequently if it's used. It adsorbs things from the water and gets full. But it is not needed full time, it's main use it to remove medication once treatment has finished. The best thing to do with carbon is keep some in the cupboard and fill the space in the filter with sponge or ceramic, whatever else is in there.

Claudie said:

Thank you for you reply. So tomorrow I’m going to do a clean , so if I do a 50% change and I use an electric vacuum too which I always use , and give the glass a good clean. So the water I use is tap water do I put the tank safe in the water before I put it in the tank?? I’ve taken a photo of my filter and I always clean the sponges out in the dirty water. I put up. Photo of the lighting too , can you tell me if it looks ok?

Click to expand...

What do you mean by electric vacuum?
If you use a gravel cleaner that sucks the gunk out of the gravel and traps it in a bag while the water gets returned to the tank, do not use it because Cyanobacteria goes straight through the bag and ends up spreading throughout the tank. Get a basic model gravel cleaner like the one in the following link and drain the gunk into a bucket that gets poured outside on the lawn or garden.