Gravel depth?

[CV26]

Our aquarium base is about 60cm x 40cm. To support the rocks we've put in and to also bury the plant roots well we laid a base of about 4-5cm of gravel. The rocks are nice and stable, and the plants seem to be doing well despite not having a soil substrate. (We were told by the LFS that we could get away without one - all seems ok for now and the plants have been in for almost 2 months)

It's pretty fine gravel - not pea sized, much smaller, but not as fine as a sand.

I've heard that gravel can trap dodgy gases as stuff not picked up by the gravel vac can get down into deeper layers and fester. If a gas bubble is released it can then cause a lot of problems for the fish.

Have we laid our gravel too thick? Is this a real risk? If it is, is there anything we can do to keep the gravel as it is but avoid this build up?

Having just started to stock up with fish, I really dont want to stress our new residents out by doing big tank design changes so ideally if we could keep it as it is that would be great, but I'm keen to hear thoughts.

 

[Byron]

The gravel depth is fine. Much of the "talk" about organics being trapped in the substrate and killing fish is misleading. I'll come back to this momentarily.

Plants do not need soil, regular fine gravel or sand is best. You can always use substrate tabs for larger plants (swords really benefit from these), and/or liquid fertilizer that is comprehensive (complete, containing all necessary nutrients).

Rocks...make sure these are actually on the glass floor of the tank. Many fish will dig into the substrate, and the natural thermal movement of water can shift the substrate on its own. If rocks are piled or stacked, the bottom one if not on the glass could shift and bring them down, cracking the glass. The bottom rocks should thus always be touching the glass with the substrate placed around it. Smaller pebbles like river rock can sit on the substrate, provided they are not too large and not stacked.

Now back to the substrate...this is the most important biological component in the aquarium, much more important than the filter. A substrate provides the biological bacteria bed for many species of bacteria. Some are aerobic, requiring oxygen, some are anaerobic, some are facultative anaerobes that can use oxygen or not, depending. All of these are important and together create a healthy substrate which really is the foundation of the aquarium's biological system.

It is OK to vacuum into the substrate along the front and where there are not rocks, wood or plants rooted. But these areas should be left alone. There will be anaerobic areas under wood and rocks, but they will complete the nitrification/de-nitrification processes. But you don't want to dig into them or you might have problems; just leave them undisturbed. Some of the sand substrates in my tanks are never touched, for years. Plants rooted in the substrate will release oxygen through their roots. Another benefit are the Malaysian Livebearing Snails that burrow throughout the substrate.

Anaerobic areas are more likely in deeper substrates, say 4 + inches (10 + cm). My sand or fine gravel substrates tend to be about 2 to 2.56 inches (5 - 7 cm) depth when spread over the empty tank; some substrate along the front can then be pushed back, with rocks or wood, to sort of terrace the substrate. It will shift a bit over time anyway.

 

[CV26]

Thank you for your reply, that's reassuring.

As a beginner there is so much information out there, Each aquatics shop we visit has slightly different advice, and every google search throws up horrible stories - it can be easy to focus in on the bad stuff and forget to enjoy the hobby.

 

[Byron]

Thank you for your reply, that's reassuring.

As a beginner there is so much information out there, Each aquatics shop we visit has slightly different advice, and every google search throws up horrible stories - it can be easy to focus in on the bad stuff and forget to enjoy the hobby.

When it comes to stores, unless you absolutely know the individual that he/she is truly knowledgeable in the hobby, it is wise never to take their advice without researching it. And yes there are reliable and unreliable sites/sources online. Which is why a forum like TFF is so valuable; there are many members here, and advice is "peer reviewed" and you cannot do better than that.