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Discussion Starter · #1 ·
Okay, so I'm planning on switching my black sand to pool filter sand in my 125 gallon tank. The problem is, I don't know where to start. It's a well established tank and lots of fish (about 30) sub adult/adult fish. I'm scared of big swings in my water chemistry. Do I try and save the tank water? Will it start a new water cycle? Do I put my fish in a small tank with my filters while I'm doing the change? Lots of questions that may seem a little silly but my wife wants white sand and I've never done this in a established tank hahaha. So any help and direction is greatly appreciated! I know how to clean the sand, etc but has anyone made substrate changes in a large established tank? If so please help guide me lol :p
 

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I switched out a 120g full of crushed coral and replaced it with playsand.
I put about half of the crushed coral into bags made from the wife's nylons (don't tell her), and left the bags in the tank with the new sand for a month or so.
Not sure if it made a difference, but I never had any issues with switching over.
 

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There are a couple different methods that people use to switch out substrate in a stocked tank.

1) Remove fish to a temporary tank with the filter. Remove rocks and decorations. Remove water and use a dust pan or similar container to remove substrate.

2) Leave the fish in the tank. Remove rocks and decorations. Use a hose to siphon out the existing substrate into 5G buckets; this would be similar to doing a water change and can be done over the course of a few days. Repeat until all the old substrate has been removed. I've used this method with success and is my preferred way to avoid having to move the fish. I use a large diameter clear vinyl hose with a PVC barb fitting and a length of PVC pipe as the vacuum, easy to handle and it reaches into the tank well. You just need to keep an eye to avoid overfilling the bucket with water. :) It takes longer than the 1st method but it works for me.

Be sure to rinse your new substrate before adding to the tank to remove any dust or small particles. I use either a large scoop or an NLS empty food bucket to add the new substrate to an existing tank that is half full of water. You may want to briefly shut off any filters until the substrate has settled.
 

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Discussion Starter · #4 ·
Thanks peeps, that helps alot.

Deeda, looks like I'm gonna try method #2 due to not really having am adequate extra tank for all my fish.

Ill plan on doing it over the course of a few days to avoid big swings in water parameters. With that being said, did you add fresh water everyday (to keep the tank water level full) while taking out the old sand? Or did you allow it the tank to slowly go down in water levels with the fish in the tank. Sorry for all the questions, just wanna make sure I do it right to ensure that I save all the fish and keep the stress level low
 

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Yes I added fresh water every day, enough to fill the tank back up to full, just remember to treat your new water first and relatively close to tank temperature. I usually do 50% water changes weekly on my tanks so the 1st substrate removal with water was about 50%.

If you usually change less water, try and do the same. Monitor your fish for unusual behavior or stress. I never noticed fish changes during this process.

On a side note, my tank had canister filters on it and I was able to leave them running while doing the substrate/water removal process. Just be sure the water level doesn't drop below the intake strainer or if you notice the canister isn't operating properly. Power filters (HOB) need to be turned off during the process and probably primed before starting back up.

You should not experience the need to cycle the tank again using either method on a mature tank. Water changes should not affect the cycle!

You could even move your rocks and decor to 1/2 of the tank, remove substrate on the other and then the following day switch sides. Or divide it in 1/3's or 1/4's, whichever you want to try.
 

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Discussion Starter · #6 ·
Perfect! I have and Fx4 and aqua top canister filter with a powerhead....so plenty of filtration and movement. This helps a ton. Thanks for advice! Will post before and after pics
 

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I have a 75 gallon planted tank and over the past couple weeks I have been wanting to change to a dirt substrate to benefit the plants. Right now I have in 100 lbs of black diamond blasting sand, which probably holds a good amount of the bacteria. I also run 2 canister filters, a Rena filterstar Xp3 and a Eheim, both loaded with media.
I have 4 roselines
2 corys (had more but died)
5 red eyed Tetras
3 black skirt Tetras
It is pretty lightly stocked because I was short on money,
I want to take out the black diamond blasting sand and out more of a beach sand so my tank isn't so black
Will this cause way to much of a mini cycle? Even if I add a bottle of safe start ? Anyone ever attempt this before ?
 

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If your filters are well established, you should be fine. Don't scrub the glass or décor as they also have bacteria.
 

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Lukas, you mentioned wanting to change to a dirt substrate so that process would be a bit different that just changing a hard substrate. Tanks that use dirt or soil are are done prior to adding water to avoid all the fines getting in the water column.
 
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