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Here are our considered answers to your problem enquiries.

We hope that you will find them of value but we can't guarantee success - there are just too many variables in fishkeeping (especially if there's a vital fact you omitted to tell us in the first place!)

If you disagree with our suggestions, or know of a better remedy, we offer you space on these pages for your point of view too.

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I was hoping that you might be able to give me some advice on a problem I have with my pond. I have had a new filter installed and am having it enclosed in the same brickwork as the pond itself. Obviously it is right up beside the pond and I am rather concerned that cement may fall in when the bricks are being laid.

Could you please tell me whether there is any special cement on the market that is not harmful to Koi or Goldfish, as to remove them all before hand would be very difficult for me and extremely stressful for them. Many thanks for your help in this matter.
Kindest regards, Pam England (Mrs)

Obviously you can use water-proofing additives in cement but that's not what your concern is about. I don't know of any 'Koi-safe' mortar or cement I'm afraid but this should not worry you unduly.

As the pond contains Koi I am assuming that it's of generous proportions.
Compared to the total volume of water a few dollops of misdirected mortar should not adversely affect water conditions too much.

Once the brickwork of your new filter enclosure is finished, it can be rendered and then sealed with something like G4 to prevent any lime leaching out of the mortar.

On a practical note, maybe you could drape a large sheet of plastic across the edge/end of the pond where the construction is occurring then any cement that drops would be caught before it reaches the water? Just a thought.

Your fish should soon be feeling the benefit of your new filter, but remember that it will take a little time to mature even if you 'seed' it with some of the existing filter medium.


Hi there,

I have a 1400 litres Koi pond and just used Tetrapond Algofin to kill some blanket weed.
The water went from crystal clear to a very muddy brown colour over night is this normal?
How long will it be till it goes back to normal? Thanks for your help, Tom.

You have touched on an aspect of algae control that is often not appreciated by fishkeepers.
Most algae control agents either deal with the algae by killing it off, causing it to lump together into floating rafts or making it sink to the bottom.
In some cases, the algae may also be encouraged to form degradable 'silt' which, unfortunately, your Koi will have no problem in stirring up to discolour the water!

In every case the affected algae must be removed from the water as any decomposition of it will cause oxygen depletion to the detriment of the fish.

Always refer to the manufacturer's recommendations when using remedies. It may be that if your Koi pond is fitted with a suitable filtration system this will clear the water fairly quickly anyway.


I have a small guppy fish that I got just today from my science teacher.
I do not know what kind of guppy I have. It has two black eyes and a little bit less than an inch. Its colour is grey too.

My guppy is put into a small milk carton and my teacher put water without chloride. My guppy looks similar to this picture, but it is much smaller and does not have colour on it. I think it is a baby.
Its eyes are only two dots without a corona. Could you please send a picture of the guppy you think I am talking about. It also has a skinny tail. It is not spread out. It also looks like a tadpole.

I do not have a tank.
I do not have its food.
I do not know what plants it eats.
I do not know what kind of fish I have.
I do not know if I have to put it under light or not.
I do not know if it is a male or a female.
I do not know how to take chloride out from water.
I do not know what other kinds of food it eats than plants.
I know it eats algae, but what kind?
I do not know how big of surface it needs.
I do not know if it is pregnant or not.
What about sickness?
What do I do if it is pregnant or sick?

Hopefully you will know what fish I have from my description and send a picture and info.
Thank you sincerely, Meera

What a lot of questions!
Let's start off by saying it is not possible to give your Guppy any particular type name because all male Guppies are different to each other. You can tell if it's a male (and it sounds like it is) by looking at the fin underneath the body: if the fin is fan-shaped then the fish is female but if the fin looks more like a pencil then it's a male. (see the
Know Your Fish article on the Really Useful Page on this website)

You will care for your Guppy best by giving it a tank to live in. It won't need a very big tank (unless you're planning to add more fish) and something 30cms long by 25 cms high 25cms front to back will do fine.

As the Guppy comes from tropical waters you will need a heater and thermostat unit to keep the tank water at the correct temperature. A covering hood with a small light fitted in it will help make the tank look nice and any water plants to grow. Complete aquarium kits (of all sizes and prices) can be found at your local aquarium store.

Guppies do not eat plants although they might nibble at the algae on them from time to time. You can get proper fish flake food at your store too.

You can take any chloride (chlorine) out of the water by using products called something like Tap Safe or Aquasafe; all you do is add the correct dosage to any water you want to use in your aquarium.

If your fish is a male, then it won't become pregnant and if it is a female then it will only give birth to baby Guppies if it was pregnant when it came from the shop. You can tell when a female Guppy is pregnant as her tummy gets bigger and a dark patch appears near to her vent just in front of the single fin under the body.
If your aquarium has some bushy plants in it, when a pregnant Guppy gives birth the young babies can hide in the plants and not get eaten by their mother (sorry, but this kind of thing does happen).

It is unlikely that you fish will get sick if you follow these actions.

1. Never give more food than the fish will eat in two or three minutes.
    Any uneaten food will make the water dirty.
2. Change some of the aquarium water every three or four weeks - say around 10-15%.
3. Leave the tank lights on for about 10-12 hours each day, especially if there are plants
    in the tank.

The most common illness fishes get is something called White Spot Disease. This is easily recognized - look for lots of very tiny white spots on the fish's body and fins - but is easily treated using a remedy available at your store.


I have 3 goldfish in an outdoor pond. They have been very well.
Just over a week ago, the pond was attacked by an unknown animal, probably a cat, which jumped on the net. The weight of the animal pushed the net right down into the pond.
The animal obviously got out the pond and escaped.

The fish seemed to be okay and intact. However, since then, one of the fish is behaving strange. It is staying under the greenery all the time. It isn't coming up for food as the other 2 are doing and is constantly separate from them, whereas in the past, they were always swimming around together. I'm worried in case it has been injured in some way but can't get a good enough look at it to see. What do you suggest?

Your fishes have been frightened by the intrusion into their pond - a typical case of heron attack by the sound of it, a not uncommon occurrence at this time of year when herons are breeding and on the lookout for food for their young.

It appears that some of your fish recovered from the shock quicker than the other one but, given time (and it can take a week or two), it should venture out to eat once again.

Try feeding some fast sinking type of food (granules) so that the fish does not need to surface to feed from floating flake, or stick type foods. Obviously if it has really hidden away, and you think it might be injured, then you should investigate a little closer and recover it for possible treatment. Otherwise, it's a case of being patient.


Please could you tell me if "Sea Monkeys" and "Triops" (a new craze apparently), are the same as Brine Shrimp, and can they be fed safely to freshwater tropical fish?
The Sea Monkeys and Triops can be hand reared, and I am wondering if this would be safer for the fish, in regard to them catching parasites. Any help and advice would be gratefully received. Thanking you, Carole.

"Sea Monkeys" have been around for many years as an educational toy although most fishkeepers quickly realised that they were Brine Shrimp eggs, Artemia salina. Triops are not quite the same species and apparently can be traced back for millions of years.

Providing the usual steps are taken to rinse the food in fresh water (to remove the salt water used to rear them) I can't see why tropical fish (freshwater or marine) couldn't benefit from this meal and, as you say, this alternative living food is free of disease. The only snag is that the food is very tiny and best reserved for feeding baby fry from any breeding that you might do. It seems hard work to raise the shrimp up to adult size just for an occasional mouthful!

If you look at our 'Really Useful Page' you will find optimum details of How to Hatch Brine Shrimp, courtesy of Brine Shrimp Direct, a major supplier of Brine Shrimp eggs. They also supply quality Flake foods also based on marine sources of natural food such as plankton etc.


The lining in my pond was pierced due to tree works carried out and I need to change the liner in my pond which holds a lot of life.
I was wondering if there was perhaps a right or wrong time of year to carry out this procedure? Kind regards, Noreen Carew

To be truthful, there is never going to be a best time to re-line a pond - it's always going to be an inconvenient job! However, you are going about it correctly by considering the inmates' interest before your own.

On balance, late autumn would probably be the best time to do it; most of the active life in the pond will have slowed down, the plants will have died back and by removing the silt etc from the pond as you empty it you will ensure that there will be no build up of nutrients for the algae to feed on next Spring.

Try to keep as much of the old pond water as you can, to avoid stressing the fish by putting them into a pondful of new tap water. By all means rinse out any filter medium (again using pond water) and perhaps retain a small proportion of 'dirty' medium to seed the filter system so that it takes less time to mature once the pond is refilled again. Best of luck with the task



Three weeks ago we bought two Goldfish. We were told to buy them two at a time with a week in between. Less than 24 hours after we put them in a 30 litre tank with water filter one of them was found dead at the bottom with a very bent back. The following week we returned to the shop and purchased 3 Goldfish, one to replace the one that had died. Two days later, we found two dead, again with similar symptoms. One of them was the original fish.

We had our water tested and were told that it contained 200 parts per million of nitrates instead of the recommended 0.2 parts per million. When we first set the tank up we treated the water with aqutan as recommended. Since the second two fish have died we took the fish out and replaced all of the water. We again used aqutan. What do you think could have been causing the problem with the water?

A week since then we now have just two Goldfish left. There are the largest of the ones purchased. One of them appears to be fine. The other one however is gradually turning black. It also has a slightly red mouth and now regularly goes to the bottom of the tank for long periods of time where it hardly moves. What is wrong with our fish and what can we do to stop it? Rachel M

Sorry to hear of your aquatic misfortunes, hardly the start you could have wanted.

It sounds as if your fish have succumbed to 'New tank' syndrome and have been overcome by poor environmental conditions.

To understand this effect, you should appreciate that it takes a new aquarium quite a time to settle in and the water conditions to be stable enough to support fish. Your aquarium is quite small in capacity for Goldfish and what probably happened was that toxic substances (usually derivatives of ammonia from fish respiration, waste products and maybe overfeeding?) built up too quickly for the filter to be able to process them safely. This is why you were advised to leave a gap between purchases of extra fish, so the tank filtration could cope better with the extra load.

Treating the water with aqutan helps to make it less stressful for the fish by neutralising heavy metals and perhaps dispersing chlorine or other water treatments added by the water authority.

There should not be a problem with the water, especially if you bought the fish from a shop in your locality that uses water from the same supplier.

Goldfish do change colour, so this is not always a reliable guide to health.

We suggest that you carry out a reasonably large water change, ensuring that you siphon up any detritus (uneaten food etc) from the bottom of the tank.
Don't buy any more fish until your survivors have settled in.
Don't overfeed: just give the fish as much as they will eat within a minute or two.
It's a good idea to tell other members of the family that you've 'just fed the fish' so that other people don't follow along a few minutes later and do the same thing!
For the time being feed just once a day until the water conditions improve.
If your Goldfish are more than 2 inches or so in size do consider getting a bigger tank.
We hope this helps.


Last updated May 8th, 2005