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Adding a big layer of new substrate - issues to look out for?

Chris_Homan

Chris_Homan

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Joined
14 May 2021
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Location
St Albans
Hi All,

I have a 90l rimless tank that has been running for over three years. But despite root tabs, I feel that my substrate is just too thin, somewhere between 1 and 2 cm deep. Plants aren’t rooting well and I feel that I need to increase the substrate depth. My current substrate (forgot which brand) is topped with a thin layer of gravel. My fish are 3 German rams, 8 cardinal tetra, 5 penguin tetra, four H. Rosacea, 2 otocinclus. Water is normally 100% RO with added Seachem Equilibrium. Filter is a Fluval canister.

My plan is to add new substrate in one day and add livestock back to the tank the same day
1. Keep fish in 20l bucket with tank water, put heater in to maintain temperature. Add an airstone just in case. Add all stem plants to this bucket as well. Rosetta plants (crypts, swords) to go in an unheated bucket with tank water.
2. Remove remaining water from tank and remove as much gravel as possible but keep old substrate.
3. Add hardscape
4. Add Tropica ‘plant growth substrate’ to desired height, aiming for about 8cm at highest. Mix old and new substrate a bit so the bacteria are mixed up as well. Top off with gravel towards the front of the tank.
5. Fill with RO water to about 80% and replant the plants.
6. Start heating to same temperature as the fish in the bucket and get the filter and running again.
7. Wait until mayor cloudiness has settled and water is at right temperature. Add some store-bought beneficial bacteria to the tank just in case.
8. Put the fish back in and hope for the best.

Now, is this doable and safe? Are there issues I have to be aware off? Is Tropica substrate the right choice for this? I guess I will have to follow this up with a water change within a few days, yes?

Any tips, suggestions are more than welcome.

Thanks,

Chris
 

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Which product do you actually have? Tropica Plant Growth Substrate is designed to be a 1cm layer at the bottom that's then capped with a couple of inches of gravel. It's like a fine powder that is mud when wet. Do you mean tropica soil? The soil can be used without capping it.

If you've got an existing substrate that's meant to be capped then you don't want to mix that up with everything else - it's likely to cloud you water and settle like dust over everything in the tank.

The trouble with any active substrate is it can leach ammonia, so you need to be very hot on big water changes potentially daily for a few weeks to minimise fish risk.

Looking at your tank, I can see what you mean about the thin substrate. I imagine that's also causing you issues with using root tabs as really you want those pushed an inch down too which is tricky when it's very thin.

Your plants look like they are doing well and it seems more like you need more root space than you are worried about feeding them. I would personally top it up with an inert fine gravel straight over the top of what you already have. Hugo kamishi brand is cheap and fairly widely stocked - their 'fine gravel' is 1-2mm and I find plants root really well in it. There are a few colours so just match similar tones to what you have already and it will look natural when you get a bit of mixing.

I would rinse the gravel in small batches e.g. 0.5l in a jug or cup until the water runs clear and then slowly submerse the container and pour the gravel in near the substrate. You can then spread it and just tug gently up any plants that get buried to deeply. That will minimise any disturbance of plant or existing substrate. Don't worry about needed to mix new and old the bacteria will move itself. If you want to avoid a layer line on the front glass, slip a credit card down the front glass and push the existing gravel back slightly and then fill the gap with the new.
 
Wow, great advise. The current substrate didn’t require topping, I forgot the brand. And yes, I meant Tropica soil.

Rooting is really the big issue as you noted. I’m going with your advise and see if I can find some fine gravel. None of my local shops sell Hugo Kamishi but I’m sure that they would have something similar. Could I still use the Tropica Soil to give a few extra nutrients? Or will this spike my ammonia?
 
Keeping in mind that I haven't done this before, I think that I would carefully add the substrate with a jug without removing any water, fish or plants. After adding the substrate, I would pull the plants out of it, without needing to fully uproot them. Then I would do a large water change after everything is ready.

The way you describe, you are changing the water before messing with the substrate, that sounds inefficient.

Keep a close eye on ammonia levels and react accordingly.
 
Chris_Homan said:
Wow, great advise. The current substrate didn’t require topping, I forgot the brand. And yes, I meant Tropica soil.

Rooting is really the big issue as you noted. I’m going with your advise and see if I can find some fine gravel. None of my local shops sell Hugo Kamishi but I’m sure that they would have something similar. Could I still use the Tropica Soil to give a few extra nutrients? Or will this spike my ammonia?
Click to expand...
If you wanted to use the tropica soil, you could stick it in a bucket for a few weeks with an airline and change the water regularly so any ammonia leached out before adding it to the tank. I guess it depends how much you were adding too - an entire substrate worth will obviously be more ammonia than if you are just adding a bit at the back. The same with the gravel too - if you get it wet, then gradually lower it in a cup you can tip it out quite accurately so you could do a small amount a week and then monitor rather than all in one hit.

Any fine gravel will work, if you are thinking of adding that and the tropica, I'd go for the tropica soil powder (which is about the same size grain as a fine gravel) and then pick a gravel with dark flecks in then when you get mixing it will just look like variation in the gravel.
 
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