Water change question/poll for big tanks

[Jabba954]

And I mean 500 gallons and up.

I was just trading PMs with someone about water changes, and I said that I only do water changes when I feel it's necessary when water parameters go out of spec - which lately is about every 4-6 weeks I change 10%. This individual is adamant that regardless of tank size/water parameters, that a water change every 2 weeks is absolutely necessary. I'm just curious what you guys do (Deano, turbo, capo especially - guys who actually have and maintain large private tanks). There is undoubtedly a big difference between public aquariums and even the largest private tanks - mostly that public aquariums have teams of people to care for the tanks.

Typically, my ammonia is <0.25 ppm, nitrite is <0.1 ppm, nitrate is ~10-15 ppm, salinity 1.021sg, and pH of 8.0-8.2. I monitor every 2-3 days, and I change if nitrite/ammonia starts to climb. Usually climbing nitrate is a sign that in the next week or two nitrite and ammonia might build. I run a big 250 gallon sump with bio balls, big ol' customized skimmer, 2x 250W UV sterilizers, and a low-end sand filter.

J

 

[krj-1168]

Typically the larger tank/pond,lagoon - the less often you need to do water changes.

However larger tanks/ponds/lagoons also usually lose more water on a daily basis due to evaporation than smaller tanks do. And therefore need to be topped off every so often.

 

[TheCanuck]

well i don't have a 500plus system, but my 360 with my green has some serious bioload. I only replace water to give back trace elements. To a certain extend water changes are more than just keeping nitrates under control, they help maintain a solid PH and alkilinity in the water. Trace elements are very important. I think thats what he is trying to say. Now i don't know if that much is needed and each system varies on what elements and what needs to be replenished. I only do water changes every 3 months because my nitrates NEVER appear.... I replace trace elements with purple up and other doses. My nitrification process is so badass that i have 0 amon 0nitrite and 0nitrate all of the time. I only do water changes because i would feel rather rotten if i didn't... But i really don't have too.

BTW water changes should be completed BEFORE water params go out of spec... thus reducing stress on fish and keeping a very stable aquarium.

nice topic btw.

 

[Deano1956]

Since my pond has been up and running (900+ gallons) this past I think Nov. I have changed out maybe half of its volume. I am doing now a 50 gallon change a week, although 2 big changes where done only cause I lost it on the floor, 1 was a 150 gallon and the next was 100 gallons. My amonia looks to be 0 and ph 8.3, nitrates are 10-15 but with 6 rays I would thing nitrates will be going up. I do need more media as I have only a 75 gallon sump with live rock over the whole bottom and bioballs.

 

[Deano1956]

Just checked my amonia- .10-.15 if the API test are accurate. Which test kits do you people use?

 

[TheCanuck]

Just checked my amonia- .10-.15 if the API test are accurate. Which test kits do you people use?

API

 

[Jabba954]

Ditto - API Master Test Kit

 

[Deano1956]

sometimes i have bought these and they are like a year or two out of date

 

[capo larzo]

The only time I noticed any nitrate above 35 ppm was when I let too much water evaporate. Otherwise I flooded the basement about once a month and replaced 50-75 gallons. So less than 5% monthly kept my nitrate 30ppm or less. I'm a firm believer that nitrates are not as critical when dealing with sharks that are hardy and acclimated well. They can easily and healthfully handle 70 ppm.

 

[turbo253]

Ok just tested my water here are the results
Ammonia- total: .2 ppm and free is: .13ppm
nitrite: under .05ppm
nitrate : 30ppm
ph: 8.2

these readings all came from a seachem master kit.
I used to use the api kits but some times they seem to give me funny readings.
plus the seachem kits are much more sensitive and take lower readings. api starts at .25ppm

For filtration I use a 450lbs sand filter powered by a 1.5hp pool pump. Then on the other side of the pool i set up over flows that run into a 60 gal wet dry filter that spills into a 500 gal sump. returning that water to the pool is a pump turning over 6000 gph and a second turning over 4500 gph. Pulling out of my sump are 2 etss down draft skimmers( a 1500 and the 2500) . Its crude but seems to do the trick.lol

I am not surprised that a my ammonia is over .1ppm cause I have been pretty bad about feeding them lately. Its a lot of fun. Plus like deano's system, mine is also pretty young.

As for as water changes go, I normally end up changing between 250-500 gals every 3-4 weeks just from back washing the sand filters. Personally I think big water changes every 2 weeks or so is a waist of money. It doesn't seem to change much in my readings. Plus we are keeping sharks not coral so the trace elements in the water are not that important.
I just try to keep the ph, temp, and salinity stable and keep the o2 levels pretty high.

this seems to be working good for me so I am going to stick with it