Need some help. new fish tank

[amitnarain]

hello. im setting up a new outdoor fishtank (small raised pond).

it is 250 litres. here the temperature varies from 33 - 15 degrees (summer - winter) celcius

could u advise what kind of filter would be suited for my 250L tank.

also the different types of fish that would be alright within the above temperatures. i was thinking kois (japanese carps) but would like other suggestions. the fish would only be visible from top. no side glass. also how many fish i can put in there.

thanks

 

[theotheragentm]

You're running about 65 gallons there. A Rena XP3 Cannister filter or equivalent would do nicely on that. You could even go with two XP2 filters if you want to make sure you're getting more flow.

I will let someone else chime in on how many as the rule is generally 15 for the first goldfish and 5 gallons per fish after that, but I think that is for plain varieties of goldfish. Other fish may vary.

The low temperature will be fine for all kinds of goldfish, but be aware that their metabolism slows down greatly at temperatures around 60F or lower. If your daytime temperatures are in the mid 60's like mine are during the winter, I would say feeding lightly twice a week during winters would work.

During the summer, you may have to keep up with water changes as 90F is kind of high for coldwater fish and a small body of water like you have will heat up pretty quickly. Doing water changes to lower the temperature will help.

 

[amitnarain]

ok thanks. is goldfish = koi? can i put both together?

also i am not familiar with those filters brands etc. for my 'tank' how much water displacement filter should i buy? like 400L/h or something? i can get power filters. but dont know the displacement needed plz advise.

thanks

 

[theotheragentm]

Koi are closely related to goldfish. That's why I made the comment about the goldfish. Both can be kept together, but generally Koi keepers keep Koi only.

Since Koi are similar to goldfish, I assumed that they make heavy bioload like goldfish. Normally you want to turn the water in a tank over a couple times per hour. With goldfish I would do it more, which is why I recommended two XP2 filers or their equal in another brand. Also with two filters, you can clean one at a time so you don't remove too much nitrifying bacteria. You'd just rinse one out every other week with old tank water and hook it back up.

 

[jsoong]

65 gal is rather small for koi. They get to be 2-3 feet long and you need a minimum of 2-300 gal (1000+l) ponds for them.

For a small pond, you are limited to goldfish, even then, I would stick to small varieties (ie not 1 foot long comets). Winter temp is a bit low for the truly fancy varieties (they like to be in the low 20C at a minimum), however, you can keep common fantails & moors outdoors at those temps.

Shubunkins IMO is the best for your setup. They are single tailed goldfish, so are more hardy then the double tailed fancies. They look like miniature kois, and can be found with fancy body colours & markings just like kois. They just don't get as large as kois so are just right for a small setup.

Depending on your pond setup, you can go with a canister filter as suggested. However, since goldfish are fairly messy, you should be over filtering the tank (ie get one that is rated 2-3 times the tank size - something like 600gph or 2400 l/hr). Most pond people have wet/dry filters. Typically, the water from the pond is pump up to a wet/dry filter, then allowed to flow back into the pond with a waterfall or other decorative water feature. A wet/dry with a water fall will create much more splashing & water/air mix, which will maximize O2 exchange, and that is important in the summer .... as gold fish are cooler water fish & need to have high water O2 content (and O2 content decreases with higher temp).

Because of your high summer temp, you will need to provide shade for your fish ... things like lily pads (real or fake), overhanging rocks .... or an umbrella! Also, since this is outdoors, you might need to have hiding places (overhanging rocks most common) for your fish so they don't become food to outdoor predators. Also, with the high summer temp, there will be a lot of evaporation. You might also consider some kind of auto water topup setup, or you will be filling the pond up daily.