Can I replace substrate in a running tank

[drewsuf82]

Hey everyone!

I'm getting ready for a major overhaul of my 55 gallon tank which has been established now for about 3 or 4 years, it's going to become a planted tank for community fish (which is what it is now but it's all java fern)

The substrate I have in there now is just general good old aquarium gravel (medium sized) and I just don't like the color and how it looks and well since this is going to be a big project im trying to get things together ahead of time so I can do it all in one day (here in about a month and a half or so)

I plan on keeping as much of the water in the tank that's "established" as I possibly can but I would like to get rid of as much of that substrate (or at least BURY it) as I can.

So my questions are:

1. How much of the current substrate must I keep
2. Can I get rid of at least 3/4 of it (I figure that I am going to have to keep some to keep it from cycling
3. If I keep the current water (or a good majority of it) and don't mess with the filter bio setup will the cycle process be bad
4. Will I be able to put my fish and plants in if I basically just replace the substrate

Thanks in advance, like I said right now I'm in the planning stage and it's going to be a process getting the other things together that I want...

Alternately would it be better to just set up an entire new tank and then transfer everythin gto that tank after it's cycled and then re-do the tank and start that from scratch ?

[will5]

I just did this to my 29g this past Monday and I did not save any of my old gravel at all. I did have an a NH4 spike of 0.25 for about a day and then it went away but that was because I kept both of my old filters going on the tank without cleaning them for a few weeks beforehand.
I took all fish and plants out, drained the tank, took out the gravel, added new gravel, and then filled the tank. Then I placed plants and fish back in the tank and turned on the filters. The fish never seem to notice a thing.

[drewsuf82]

Nice! Did you use 100% fresh water when you replaced it ? I've actually been planning/wanting to do this for quite a time, but I didn't want to end up with a ton of dead fish

[will5]

Originally Posted by drewsuf82

Nice! Did you use 100% fresh water when you replaced it ? I've actually been planning/wanting to do this for quite a time, but I didn't want to end up with a ton of dead fish

No I reused about 5-7 gallons. About five inches above the substrate.

[will5]

I should add that the tank was 100% cycled by Wednesday! No nitrites or NH4 and my nitrates were @ 5ppm.

[mrduna01]

I did the same thing a while back. Lost one fish that was ill to begin with. I put fish in a bucket with old tank water. Drained, replaced substrate, filled. Just use the old filter and plan to do daily 50 percent water change for a week or so. Oh and be sure to acclimate the fish back to the tank slowly.

Sent from my Desire HD using Tapatalk 2

[drewsuf82]

Awesome thanks for the info, I have been thinking about doing this for MONTHS, I've just been afraid to make the leap although this doesn't help my case for new planted tank (hoping for shrimp) that I want to get going in the living room....I guess I'll have to find another excuse for that

[DogFish]

I recently moved my fish to a Q-Tank(20L) for a week with 75% water from the display tank(40B). Then I filled the display tank, pulled my plants & driftwood with Java ferns attached. Next I syphoned off the Black Diamond sand cap leaving the MTS undisturbed.I put on the new sand cap, replanted, returned the hardscape, filled with 100% new water. I ran the tank without fish for 5 days. Each day I swapped 5gl of water from the display tank and the Q-I also added a pinch of flake food to the empty display tank each day. On day 6 the fish went back to the display tank. They not only look good I'm seeing pre-spawn activity.











5%

[drewsuf82]

Yea doin the changes isn't a big thing for me, the tank in question is literally maybe 12 feet from the kitchen sink (im looking at doing this project with my dining room which I've converted into my office)

BTW thanks for all the replies everyone

[Complexity]

You didn't say what kind of filters you have or how much biomedia they contain, but as long as you have a good amount of biomedia in the filters, you really don't have to worry about much else.

I completely redid my 75g tank which included stripping it down and running bleach through everything. Then I added brand new substrate, new water (obviously), new plants, the whole thing. Even the decor had been bleached. So this is basically the same as setting up a brand new tank.

The only thing I did to cycle the tank was trade out one of the XP4 canisters on the 75g with one of my dirty XP4 canisters on my cycled 90g tank. I then proceeded to add around 20-25 fish.

The tank is 100% cycled. Not a single problem. All the fish are perfectly happy as if nothing had ever happened.

So you can change out all of the substrate. Also don't worry about transferring over the old tank water. Unless you have fish species that are known to be sensitive, they should do just fine with the change.

There is no big mysterious event regarding a tank cycling. It's really just a matter of the accumulation of nitrifying bacteria. For a first time aquarist with a brand new tank, the cycling process is long and arduous because they do not have a good source of bacteria to start with. So they have to wait for the trace amounts of bacteria in the water supply to enter the tank and multiply. That takes some time. However, once you have a tank going with lots of bacteria, you can use that bacteria to jump start another tank (or to keep the original tank cycled while making changes like changing out substrate). Even if you get a mini-cycle, it's short-lived and easily controlled with water changes.

I'm honestly not sure why people put such a big emphasis on keeping the original tank water because there's virtually no bacteria in the water itself. Unless the water company has made changes to the water supply, the tap water should still be about the same. We take fish from overseas in who knows what water parameters, put them in containers and ship them to LFSs who then put the fish in display tanks with different water parameters, and then sell the fish to people who put them in tanks with yet more different water parameters, and the fish somehow manage to handle it all. So moving a fish from older water to fresher water of the same parameters shouldn't be all that problematic.

[DogFish]

"I'm honestly not sure why people put such a big emphasis on keeping the original tank water because there's virtually no bacteria in the water itself"

There are a few reasons to use existing tank water.

Reduces stress on the fish as they are already assimilated to that water.

For the plants and filter system that water will have some nitrates that both can use.

A certain amount of stress is beneficial to stimulate grow in any living thing. To add excessive stress unessicarily is almost always counter productive.


.

[will5]

The reason I kept some of my old tank water is because I was changing over to Soilmaster Select, which I new would suck up anything with a + charge. And since I my old water had fertilizer in it already I decide to put them to good use because they would have gone down the drain anyway.

[Complexity]

Originally Posted by DogFish

Reduces stress on the fish as they are already assimilated to that water.

What's different between the old water and the new water? As long as the water source is the same and the temperature is the same, what's different that will stress the fish?

For the plants and filter system that water will have some nitrates that both can use.

I agree the plants can use the nitrates. So I see the validity in that (but we can easily dose nitrates with ferts). However, we were talking about fish, not plants.

As far as the filtration system, what does the filter do with nitrates? I know bacteria converts ammonia into nitrites and then converts nitrites into nitrates, but once they're converted into nitrates, that's it. As far as I know, the filter doesn't do anything to the nitrates, and there's certainly nothing beneficial about nitrates to the filtration system. That's why we have to do water changes. But if you know of something I'm not understanding, please let me know.

While I agree with you regarding unnecessary stress, I see nothing in what you've said that contributes to stressing the fish.

[Complexity]

Originally Posted by will5

The reason I kept some of my old tank water is because I was changing over to Soilmaster Select, which I new would suck up anything with a + charge. And since I my old water had fertilizer in it already I decide to put them to good use because they would have gone down the drain anyway.

Okay, I can understand that. It's more of a desire to not waste what's in the water rather than feeling the need to do it for the sake of the fish or bacteria. That makes sense.

[DogFish]

On the filter point I should have posted "nitrites" NOT nitrates. I'm getting ready for eye surgery and posting can be a challenge.

I believe a lot more goes on in the transformation from Treated Tap water to aged Tank Water on a microbial level than we understand. I have no scientific links to support that.

You may have only been talking about fish but my reference was to a tear down such I as I did. These are my thoughts just respond to your question, not tring to convince you.