New hobbyist. Please advise.

[CStrickland]

The issue with Pukani rock is two parts. It tends to have a lot of dead matter on it, which will decay over time and eventually be processed. It also tends to leach phosphates, because the actual calcium molecules of the rock itself have absorbed a great deal of it. So... the dead stuff rots and bacteria eat it, cycling the tank. But maybe it's too much and the water gets fouled. Worst case scenario the ammonia spikes to a bacteria-inhibiting level and halts the process entirely. And... even in clean water or after blasting it with a power washer, the phos continues to release for months as the levels in the rock try to match those in the water, fueling algae growth.

This is why people "cook" Pukani. Not with heat but by exporting the nutrients out of the rock itself so that it does not throw off the tank chemistry from the jump. There are many threads on cooking/curing Pukani and revitalizing it with acid to burn off the dirtier outer layer. If it were cheap and easy everyone would use it.

 

[CStrickland]

Double post, trying to fix a typo

 

[75mixedreef]

I agree that it (water changes) may be labor intensive. Given that one has a closed aquarium system and a RO/DI, how can this be more expensive than a system with a sump/refugium, protein skimmers, additional lighting and pumps, etc? Please elaborate.

Sorry, didn't check back until now because of the holiday and I forgot about this thread.

Large water changes get expensive because of the amount or salt and RODI you go through. Without any other filtering, besides live rock, you should be doing weekly 25% water changes. That's 100% a month. It depends on the size of your system, except that the equipment will get bigger with bigger systems as well, but it is almost always better to have some filtering capacity that will reduce the need to have weekly 25% water changes down to 10% biweekly or even monthly. If you can go from replacing 100% of your systems water volume a month to 10% that is a lot of savings in salt in water, especially over time.

Compare that to a 12W light over chaeto and a 13W pump on a skimmer. I did the math for my area at $0.11 per KW and it comes out to about $1 per month to run 25W for 12 hours a day. Skimmer would be on 24 hours a day so maybe $1.50 a month, but that is still way less than the amount of salt you would go through.

My example is for a 75 gallon system, I do 10 gallon monthly water changes so that's a difference of 65 gallons worth of salt. A 200 gallon salt box costs $60 at the local store. That comes out to about $20 just in salt cost, water may not be more than $1 if you make your own, but stores usually sell it for about 40 cents a gallon. The point is that you could easily be paying $20 a month in the difference there. In a year you would have paid for the cost of the skimmer and most likely the chaeto with its light. Large water changes really add up in cost and are necessary when you do not have other methods of removing those nutrients.

I might be exaggerating slightly since you might not be running an SPS system where you need those nutrients to be that low, but even at half that cost it still adds up to be way more than the running cost of equipment. Eventually you will have saved more than the cost of the equipment and the equipment will be much easier than the manual water changes.

Your purigen might work pretty well, but how efficient is it and how often does it need to be replaced? I'm sure it doesn't absorb NO3 or PO4 if it absorbs organics, plus when will it fail or when might you screw up and introduce chlorine to your system. Do you need more than one running at a time? Do you need a second set to run while you clean and dry the first? To me that seems like a lot of variables and things to go wrong that could hurt your tank instead of helping it. I know we have to look at our systems at ticking time bombs where any piece of it could fail at any time, but this one just seems too risky with too much riding on it. I would rather use it as a backup or a secondary method in case something breaks down.

 

[CFR777]

Thank you for your input guys! I really appreciate it.

I'm going to soak the Pukani rock in bleach to remove most organics, then leave it in RO water for 2-3 days to see if it leaches any phosphates. If not I'll add it to my tank. If it does leach, then I'm going to "cook" it in citric acid.

Purigen can be regenerated, therefore, theoretically, it lasts forever. I've given it much thought and read more about different types of chemical, biological and mechanical filtration. I've decided to give it a try and run my tank skimmerless. I'm going to use a canister filter (wool/sponge, purigen and carbon in that order from inflow to outflow) for mechanical and chemical filtration and a DIY reactor (rowaphos) to remove any phosphate. I was thinking of adding a DIY algae turf scrubber, but it's too much of a hassle. Theoretically I'm not going to have any problems with excessive nutrients or phosphate if I do a 10-15% water change per week. Practically, I don't know for sure. Time will tell I guess.

 

[75mixedreef]

If you add the reactor to remove phosphate, I hope you realize that you have nothing to remove nitrates. I have an algae scrubber to remover nitrogen and phosphates and a skimmer to remove excess organics. You are replacing a filter sock with the floss, the skimmer with the purigen, and some carbon in the canister. I would at least get some chaeto to soak up excess nutrients, otherwise you are counting on water changes to be your only source of nitrate export.

I know you have the purigen but that only removed organics that would decay to nitrates, anything it misses could still cause you problems. I'm also not too confident on the capacity of the purigen, its intended for biocubes. You have a 40 gallon tank with a sump, so probably double the water volume these were intended for even if they say they can work for larger systems. It also says they are for freshwater and saltwater tanks, so who knows what their filtering capacity is on the saltwater side. Freshwater takes so much less to keep it clean, which explains the 100 gallon capacity on that little pouch. I'm not trying to scare you off the purigen, just trying to get you to consider secondary nutrient removal systems.

 

[CFR777]

You're absolutely right 75mixedreef! I'm replacing the filter sock with floss/sponge as both are doing the same job, and the skimmer with Purigen. I've read that protein skimmers don't remove nitrates from water column. All they do is remove organics that can later become nitrates. It's the same with Purigen. It will remove the organics before they are converted into the toxic nitrogenous components. Both methods prevent the nitrate levels from increasing to dangerous levels. Therefore, if I place Purigen in my tank from the beginning and do regular water changes, nitrates won't build up. My tank is 30 gallons, water changes of 3-5 gallons every week won't be too much of a trouble. Also, sufficient live rock helps a lot. The anaerobic bacteria inside the rock will convert the nitrates into nitrogen gas. I understand it's a delicate balance but there's more than one way to tackle a problem.

 

[75mixedreef]

I'm still afraid that your nitrates are going to be climbing more than you would like. By all means, there is nothing in your setup that would not work. I'm just worried that you will have issues getting rid of green hair algae. Your setup could work for quite a while before the nitrates do start to get high, but when they do you have to remember that the only way for you to lower them is to do water changes.

I prefer to not have to do water changes at all. I have gone 6 months before without doing any water changes and my tank was doing great. I have 2 part and magnesium to maintain my parameters so when you get the system going well with the ATS and skimmer, all you need to do is monitor the parameters like normal and test NO3 and PO4 only when there are symptoms of issues. I run mine as more of a set and forget with spot checks and regular additives. You are aiming for more of a constant maintenance approach with the water changes, regenerating the purigen, replacing carbon and filter floss. All I have to do is clean a skimmer cup once in a while and trim the algae, it takes me less than 5 min a week. I add chemicals when I feed and that takes about 30 sec since I know how much to add. You probably have 60-90 min worth of maintenance every week before you even start testing or regenerating the purigen. I think I'll stick to my less labor intensive strategy where water changer are not the primary source of nutrient removal.

 

[CFR777]

You're probably right. Nevertheless, I'll give it a try and see what happens. Thanks for your input!