nitrate

Question
I have a 33 galllon tank, it's been set up for about 7 or 8 months, i have 2 koi (both about 7 inches long) and two gold fish(both about 2-3 inches long) and 1 small algea eater. i had a problem with my freshwater levels after an ich treatment. my ph kept dropping and my nitrate/nitrite levels were high. after many water changes, adding plants, new and better filtation(Bio-wheel good for up to 80 gallon tank), coral and chemical treatments, (such as bacterial stabalizers, amonia,nitate,nitrite remover, and ph up) i got my levels pretty good. there is no ammonia, the ph is fairly good at 6.8 and no nitrite, but i cant keep my  nitrate levels low. they go down when i do a water change( to about 10-20 parts) but then go back up after almost a week. what can i do to get rid of my nitrate. usually when i do a water change i do about 25-30% but with these problems i was doing a lot more, like 50-65%.

Answer
Hi Tammy;

A nitrate level of 10 to 20 ppm is really not bad at all, but if it goes way up (past 40) in just a few days it means there is just too much waste in the system. It's because of the type of fish you have. Koi and goldfish are very messy fish that get very big. Your koi will grow to be well over 2 feet long. They actually should be in a tank or pond of 500 gallons or larger. As they get bigger in your little tank they will get stronger and could actually break the top of your tank and get out or hurt themselves hitting the top and sides. They need plenty of room to move about and get exercise. The goldfish will grow to be about 8 inches long. The goldies are okay in the 33 gallon with the algae eater but that's about all the room there is in that size tank.

To help keep the nitrate levels lower until they can be moved, cut back on food and offer vegetables. Koi and goldfish are natural-born gluttons. They will want food all day long but you don't have to give it to them. They only need to be fed twice a day whatever they can eat from all areas of the tank in less than 3 minutes each time. Replace  at least 4 feedings a week with vegies such as cooked peeled peas, romaine lettuce, cooked green beans, shredded cooked carrots, and cucumber slices. They don't have to eat veggies within 3 minutes though. It doesn't rot like other foods do and will not make them fat like commercial pellets and flakes do. Just don't get carried away though because vegies can make a mess. Give each fish some to nibble on for a while. They really need more fiber in their diet than regular packaged foods can provide so vegies should be a regular thing all the time.

Good luck with those guys...

At Your Service;
Chris Robbins