Some info I would like to share

Some of you here remember me from the old forum and that I have Iridescent Sharks aka catfish sharks.
I have them in a 130 gallon tank that is filtered by a home-made 10 gallon tub filter.

Now, I used to get told that I would always have to do weekly 50% water changes to keep the ammonia & nitrites at bay.
I unfortunatly have been a bit lazy in that department. I recently went out and bought the API freshwater master test kit. The last water change was done 3 weekends ago. Nitrites are at 0ppm along with the ammonia at the same level. One would think that after a week, one would be higher than 0. But that is not the case at all. Maybe it takes longer for these to build up, or my filter is working pretty damn good. Surely, the results should be higher after 3 weeks?
Tank is kept at 77 degrees F away from any sunlight. My fish are healthy, even the smaller one that got really sick back when I moved him to the 125 gallon tank, where he turned a puke green.

What I am getting at, is weekly changes may not be as necessary as once thought for these guys. Even the snail issue is pretty much cleaned out without any real doing by me.

Thoughts?

A major question would be the nitrate levels in the tank after 3 weeks of no changes?

I would never advocate for less frequent or smaller water changes in this case (or in almost any case).

What are the nitrates at?

I don't test, but do large water changes religiously. When I slack, I see sluggish fish, loss of colour, algae outbreaks, discoloured water (sometimes) and a host of little things. Purely anecdotal, I know.

Since I am a fish breeder for fun, I also see much less breeding in non swamp fish species. One of the things we can't measure with those basic test kits is hormones released by the fish into the water, a possible factor in a tiny closed system like any of our tanks.

You had a huge number of problems with those fish. You don't now. That's good news. So back to the old regime?

0 ammonia and nitrite is an indication that your biological filter is working well. With the final step in the nitrogen cycle being the production of nitrate, after 3 weeks of no water change, your level must be very high. With your size of fish and tank, nitrate creep would be in the order of 5ppm daily, give or take a bit. After 20 days you have 100ppm nitrate. Thats a lethal level. Major key to getting an accurate reading with the API kit is to shake the b'jeepers out of bottle #2. It has zinc crystals that must be thoroughly dislodged. It takes prolonged exposure to toxins to kill or make fish seriously ill. You may have gotten away with a 3 week water change lapse, but continuing that sched will kill your fish.

I was always under the impression that ammonia & nitrites were the most important ones to test for. Anytime I had a test done for me at Big Al's, I don't think they tested nitrates.

As for the water change, I wasn't planning on going beyond this weekend.
As for the nitrate test, it is high.

Nitrates are toxic, but not at the level of ammonia. Ammonia and nitrites are converted by a good filter, then you and the plants deal with the nitrate. That's the major reason for water changes.

I recently injured my ankle and foot, and that set me back a bit - I went 18 days with no water changes. Nothing died. Since I regained my mobility, I have been VERY careful to stay on schedule. I know I had my poor fish living in sub-standard conditions, and their residual health got them through. I don't want to expose them to those conditions again.

if your system is properly sized, stable and a reasonable fish load the Ammonia and Nitrites will be metabolize by the bacteria in your biofilter. The fact that your levels are good for both is a good indication that all is well.

The main purpose for the water changes is to get rid of the Nitrates in your system. There is no bacteria that will get rid of this. In a planted system the plants will us some of these up. As an example I don't do any water changes in my ponds. They are covered with plants that do a great job of absorbing/using up the nitrates in the ponds. I can actually tell by looking at the plants how the Nitrates are doing. If the plants are growing great and nice and green there is certainly some level of Nitrates in the water. If the plants are kind of pail and not growing well there is probably not much in the water for them to grow on. This is why for propagation purposes I grow my pond plants in tubs, there is just not enough nutrients in the water with my fish.

So the end result is you need to do water changes to get rid of the Nitrates in your aquarium water. They are not as deadly as the Ammonia and Nitrites, but they will kill your fish if the levels are left to rise.

Steve

There are also other harmful elements in water beyond the usual 3. TDS, phosphates, silicates. Obviously more relevant with bigger fish. You have to consider that fish live in their own toilet and the system must be flushed with clean water.

Suprd71 wrote:There are also other harmful elements in water beyond the usual 3. TDS, phosphates, silicates. Obviously more relevant with bigger fish. You have to consider that fish live in their own toilet and the system must be flushed with clean water.

That is a great comparison!

I used to have a couple Amazon Swords in that tank. Maybe I'll grab a few again. Just have to make sure there's no snails hitchhiking.