Plugging holes in a saltwater tank?

[Motörcrab]

I just picked up a 48x12x21 saltwater aquarium on craigslist for a pretty good price. It has the plastic cover sealed from the rear to side wall in the one corner and two holes in the bottom behind the cover, the holes are roughly 1 1/4 diameter each. At first I thought plexiglass and silicone, but after reading the forums several people said NOT to use the two together because of the possibility of failure down the road.

I am thinking carefully using a flat razor to scrape the silicone to remove the cover. Then to patch the holes is to get two pieces of 5"×5"x1/4" glass cut and put one on the bottom and one on the inside of the tank with aquarium silicone. On the closest edge of the hole to the existing silicon it will give approximately 3/4" to use as a sealing area.

Does everyone thing that will create a lasting bond that won't leak in the future? Are two plates overkill? Will taking some sandpaper to the glass make a better seal or not? Are all aquarium sealants basically the same or is there one that is better then the rest?

Thanks in advance.

Attached is a photo for a better reference.

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[aussieJJDude]

Have you thought of using this as a bulkhead to remove excess water from the tank, in case of flooding?
A glass cover siliconed on top will work, as long as its aquarium safe silicone its fine. No need to sand.


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[wodesorel]

You don't need it to stay watertight since it won't be holding water. You just need to spread the weight of the sand out so it doesn't put too much uneven pressure around the holes, and so the sand doesn't fall through. I'd razor blade it smooth and go with a thick chunk of plastic or plexi siliconed in place, myself.

[Motörcrab]

I never thought about using that as a bulkhead. Pretty much convert one hole to be a drain and access it from the bottom if I do get flooding? Or plug both holes and leave that section blocked off so If it does flood the water will build up there and can use a sponge or rag to collect the excess water that builds up? Please explain more!

Now you got my gears in my head turning to have a safety back up.

We never experienced flooding in our tanks but, we have only been using a few inches maybe 3" of straight Zoo Med Eco Earth coconut fiber in both tanks using a wire tops and plastic wrap over the tops. They have never built up excess condensation to the point they flood. I'm assuming the coconut fiber dries out quicker compared to the sand/fiber mix? We have have been wanting to do the 5:1 mix of playsand (my friend works at Quikrete and can get it for free) and Coconut fiber to make it deeper and to give the crabs better digging and molting options. I imagine adding the saltwater to the mix would help with humidity levels as well. I currently mist the fiber once or twice a day and it seems to keep the humidity in the safe zone 70-85% with occasional drops into the high 60% between mistings. Come winter and our windows are closed I believe the humidity can pose an issue.

Anyway before I keep rambling on, With changing to the sand/fiber mix is there a greater chance to "flood" the tank compared to what we are currently doing with the straight fiber? I will continue my research on tank flooding now. I always try to look through older topics before I post incase things have been repeated over and over again. lol

[aussieJJDude]

Yeah, pretty much. A bulkhead, few pieces of pvc and maybe a small bucket to catch any excess water. Good if you decide to mist heavily, simulate tropical rain or use humidifiers.
Or you could even use it as a built in and then automatically change the water through a ball valve.. ¯\_(ツ)_/¯

Coconut fiber is really good at soaking up excess moisture, while sand is better for drainage. However, ee doesnt hold up tunnels as well as sand. As a result, we reccomend a mix so you get the best of both worlds. The 5:1 id meant to mimic beaches in the wild, which contains a bit of organic matter.

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[Motörcrab]

This is why my wife (xenocrab) hates when I do "research" for the crabs, or anything else for that matter. I will explore every possible option before deciding on, IMO the best solution. I can easily turn something as simple as plugging a hole into a larger more complex project. Not to mention all the time researching and getting sidetracked with something completely unrelated! lol! But hey, it's for the benefit of the crabs right?

[soilentgringa]

This is why my wife (xenocrab) hates when I do "research" for the crabs, or anything else for that matter. I will explore every possible option before deciding on, IMO the best solution. I can easily turn something as simple as plugging a hole into a larger more complex project. Not to mention all the time researching and getting sidetracked with something completely unrelated! lol! But hey, it's for the benefit of the crabs right?

I noticed in a previous post you said you have E's. I would definitely recommend at least 12" of the cocofiber plus playsand substrate. E's dig a lot and they have been known to cannibalize molters.

I personally have not had any deaths that could be traced to my 3 E's, but they have quadrupled in size since we got them, and they dig constantly. Other crabbers have had some bad luck with their Eccies.



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[Motörcrab]

We will have to discuss how deep we want to go with our substrate. Especially since it will be our first time mixing and I'm sure there will be a learning curve as well.

So if I did my calculations right, correct me if I'm wrong. According to the Quickrete calculator www.quikrete.com/calculator/main.asp#playsandcalculator
For the tank 48 X 12 X 21 we would need about 9-10 bags of playsand to get to a 12" depth and about 2 bags of Coconut Fiber mix. That would put the total weight of the tank to about 525 lbs! Roughly 450 lbs for the substrate mix and saltwater another 75 for just the tank!

What is the best procedure to start mixing since it will need to be done in a 5 gallon bucket then carried to and dumped in the tank. Are there any rough calculations like 10 pounds of sand to 3 cups of water to help with mixing? I know it will vary due to the starting point of the sand. I'd rather add water later instead of trying to remove it.

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[wodesorel]

I've had to use anywhere from 1/2 to nearly 2 gallons of water per bag of sand. Grain size and moisture levels will impact how much is needed. Experiment a bit with the first batch and you can start an assembly line after that.

As for the Eco earth, I recommend using half the water suggested, make it hot, and then cover the bucket with plastic wrap and let it sit for 20 minutes. You may or may not need to add more water, but it helps from turning it into soup from the start!

The dimensions you gave is of a 55 gallon tank. For mine, I used 4 bags of sand and two cocofiber blocks to get to 10-11 inches.

[Motörcrab]

2 bags of sand is a lot better than 10! The Eco Earth we have been using is the loose that comes in the .8 Cu Ft, 23 liters bags. I'm guessing I add 5:1 mix of fiber and sand first, then add the water to the right consistency?

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[soilentgringa]

2 bags of sand is a lot better than 10! The Eco Earth we have been using is the loose that comes in the .8 Cu Ft, 23 liters bags. I'm guessing I add 5:1 mix of fiber and sand first, then add the water to the right consistency?

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I have 5 bags of sand in my 55. Used 1/2 brick of EE for each bag, and one brick on top of the sand.

Substrate is really not something you want to skimp on. They tunnel, dig, and make caves underground to molt, and the more sub you have, the less likely it is that you'll have molt attacks.



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[soilentgringa]

I've always just mixed mine in a large tote or in the tank itself.

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[wodesorel]

One block equals one bag, if that helps.

I love the concrete mixers from home Depot. It was I think $6, is heavy plastic, and gives a large waterproof work area to mix. For aquariums I've never had trouble mixing in place, but it can be awkward if you have to stand on a stool or anything like that. I did do the sand for my 10 in a bucket so I wouldn't dust up my bedroom.

[soilentgringa]

One block equals one bag, if that helps.

I love the concrete mixers from home Depot. It was I think $6, is heavy plastic, and gives a large waterproof work area to mix. For aquariums I've never had trouble mixing in place, but it can be awkward if you have to stand on a stool or anything like that. I did do the sand for my 10 in a bucket so I wouldn't dust up my bedroom.

I enlist the kid to help me scoop when I use totes to mix.

He hauls sand till his arms are like to fall off then we take breaks.

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[Motörcrab]

Thanks, that does help for an idea of what we will be getting into. I'm thinking our first task will be to plug the holes in the 55 gallon tank.
I'm also thinking that since we are looking for a new crabitat to call our own it may be smart to hold off on setting up the 55 gallon tank until we actually move. I don't see the point in getting that big of a tank set up only to tear it apart in a few months, then repeat.
Until then we will add additional substrate to our existing tanks. That way we can use our feelers to get an idea on the bigger tank.

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